2024-03-28T18:15:54Z
http://eprints.adm.unipi.it/cgi/oai2
oai:eprints.adm.unipi.it:156
2010-12-20T11:16:04Z
7374617475733D756E707562
7375626A656374733D417265613031:494E462F3031
7375626A656374733D417265613131:4D2D53544F2F3038
74797065733D636F6E666572656E63655F6974656D
http://eprints.adm.unipi.it/156/
Dentro gli openUrl resolver: magie e limiti
Bucchioni, Cinzia
INF/01 - Informatica
M-STO/08 - Archivistica, bibliografia e biblioteconomia
Una rassegna delle degli sviluppi, delle realizzazione e delle problematiche relative alla tecnologia degli openresolver e allo standard Openurl (Niso Z39-88)
2005-11-11
Conference or Workshop Item
NonPeerReviewed
application/pdf
it
http://eprints.adm.unipi.it/156/1/SFX200510-2.pdf
other
it
http://eprints.adm.unipi.it/156/2/SFX200510-2.ppt
Bucchioni, Cinzia (2005) Dentro gli openUrl resolver: magie e limiti. In: [Seminario Annuale del Caspur], 10-11 Nov 2005, Napoli, Italia. (Unpublished)
oai:eprints.adm.unipi.it:162
2010-12-20T11:15:44Z
7374617475733D756E707562
7375626A656374733D417265613031:494E462F3031
7375626A656374733D417265613131:4D2D53544F2F3038
74797065733D636F6E666572656E63655F6974656D
http://eprints.adm.unipi.it/162/
Lo standard Openurl: evoluzioni e applicazioni
Bucchioni, Cinzia
INF/01 - Informatica
M-STO/08 - Archivistica, bibliografia e biblioteconomia
Una rassegna delle degli sviluppi, delle realizzazione e delle problematiche relative alla tecnologia degli openresolver e allo standard Openurl (Niso Z39-88)
2006-03-03
Conference or Workshop Item
NonPeerReviewed
application/pdf
it
http://eprints.adm.unipi.it/162/1/SFX200603.pdf
other
it
http://eprints.adm.unipi.it/162/2/SFX200603.ppt
Bucchioni, Cinzia (2006) Lo standard Openurl: evoluzioni e applicazioni. In: Seminario monografico AIB-Lazio, 3 Marzo 2006, Roma, Italia. (Unpublished)
oai:eprints.adm.unipi.it:533
2010-12-20T11:26:27Z
oai:eprints.adm.unipi.it:534
2010-12-20T10:54:34Z
7374617475733D696E7072657373
7375626A656374733D417265613031:494E462F3031
74797065733D61727469636C65
http://eprints.adm.unipi.it/534/
An Intermediate Language for Stochastic Simulation of Biological Systems
Barbuti, Roberto
Caravagna, Giulio
Maggiolo-Schettini, Andrea
Milazzo, Paolo
INF/01 - Informatica
We introduce Stochastic String MultiSet Rewriting (sSMSR), and propose this formalism as an intermediate language for the simulation of biomolecular systems. Higher level formalisms for biological systems description can be translated into sSMSR, and the features of sSMSR allow the development of efficient simulators. In this paper, we show the encoding into sSMSR of two formalisms for the description of biological systems, namely Stochastic CLS and the Stochastic π-calculus. We prove soundness and completeness of both the encodings.
2008-07-01
Article
PeerReviewed
application/pdf
en
http://eprints.adm.unipi.it/534/1/sSMSR.pdf
Barbuti, Roberto and Caravagna, Giulio and Maggiolo-Schettini, Andrea and Milazzo, Paolo (2008) An Intermediate Language for Stochastic Simulation of Biological Systems. Theoretical Computer Science . ISSN 0304-3975 (In Press)
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V1G-4THSX7T-8&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=5cba2c034486cefb4890cd306f4d8dce
doi:10.1016/j.tcs.2008.09.032
oai:eprints.adm.unipi.it:552
2010-12-20T10:54:13Z
7374617475733D696E7072657373
7375626A656374733D417265613031:494E462F3031
74797065733D61727469636C65
http://eprints.adm.unipi.it/552/
Efficient inclusion for a class of XML types with interleaving and counting
Colazzo, Dario
Ghelli, Giorgio
Sartiani, Carlo
INF/01 - Informatica
SUMMARY: Inclusion between XML types is important but expensive, and is much more expensive when unordered types are considered. We prove here that inclusion for XML types with interleaving and counting can be decided in polynomial time in the presence of two important restrictions: no element appears twice in the same content model, and Kleene star is only applied to disjunctions of single elements. Our approach is based on the transformation of each such content model into a set of constraints that completely characterizes the generated language. We then reduce inclusion checking to constraint implication. We exhibit a quadratic algorithm to perform inclusion checking on a RAM machine.
2008-02-01
Article
PeerReviewed
application/pdf
en
http://eprints.adm.unipi.it/552/1/GheColSar08-is.pdf
Colazzo, Dario and Ghelli, Giorgio and Sartiani, Carlo (2008) Efficient inclusion for a class of XML types with interleaving and counting. Information Systems, Availa (Availa). ISSN 0306-4379 (In Press)
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V0G-4TRK0V5-1&_user=10&_coverDate=10%2F22%2F2008&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=69b8593f369ace293c66acdf838f7f84
doi:10.1016/j.is.2008.10.001
oai:eprints.adm.unipi.it:596
2010-12-20T10:51:59Z
7374617475733D707562
7375626A656374733D417265613031:494E462F3031
74797065733D61727469636C65
http://eprints.adm.unipi.it/596/
Hierarchical, model-based risk management of critical infrastructures
Baiardi, Fabrizio
Sgandurra, Daniele
Telmon, Claudio
INF/01 - Informatica
SUMMARY Risk management is a process that includes several steps, from vulnerability analysis to the formulation of a risk mitigation plan that selects countermeasures to be adopted. With reference to an information infrastructure, we present a risk management strategy that considers a sequence of hierarchical models, each describing dependencies among infrastructure components. A dependency exists anytime a security-related attribute of a component depends upon the attributes of other components. We discuss how this notion supports the formal definition of risk mitigation plan and the evaluation of the infrastructure robustness. A hierarchical relation exists among models that are analyzed because each model increases the level of details of some components in a previous one. Since components and dependencies are modeled through a hypergraph, to increase the model detail level, some hypergraph nodes are replaced by more and more detailed hypergraphs. We show how critical information for the assessment can be automatically deduced from the hypergraph and define conditions that determine cases where a hierarchical decomposition simplifies the assessment. In these cases, the assessment has to analyze the hypergraph that replaces the component rather than applying again all the analyses to a more detailed, and hence larger, hypergraph. We also show how the proposed framework supports the definition of a risk mitigation plan and discuss some indicators of the overall infrastructure robustness. Lastly, the development of tools to support the assessment is discussed.
2009-09
Article
PeerReviewed
application/pdf
en
http://eprints.adm.unipi.it/596/1/baiardijournalrevised.pdf
Baiardi, Fabrizio and Sgandurra, Daniele and Telmon, Claudio (2009) Hierarchical, model-based risk management of critical infrastructures. Reliability Engineering & System Safety, 94/200 (9). pp. 1403-1415. ISSN 0951-8320
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V4T-4VK6N7F-5&_user=793840&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000043460&_version=1&_urlVersion=0&_userid=793840&md5=f5618c7ce18bfdacd6d4c8b9d177e713
doi:10.1016/j.ress.2009.02.001
oai:eprints.adm.unipi.it:610
2010-12-20T10:50:51Z
7374617475733D707562
7375626A656374733D417265613031:494E462F3031
74797065733D61727469636C65
http://eprints.adm.unipi.it/610/
Transparent Process Monitoring in a Virtual Environment
Sgandurra, Daniele
Maggiari, Dario
Tamberi, Francesco
Baiardi, Fabrizio
INF/01 - Informatica
PsycoTrace is a system that integrates static and dynamic tools to protect a process from attacks that alter the process self as specified by the program source code. The static tools build a context-free grammar that describes the sequences of system calls the process may issue and a set of assertions on the process state, one for each invocation. The dynamic tools parse the call trace of the process to check that it belongs to the grammar language and evaluate the assertions. This paper describes the architecture of PsycoTrace, which exploits virtualization to introduce two virtual machines, the monitored and the monitoring virtual machines, to increase both the robustness and the transparency of the monitoring because the machine that implements all the checks is strongly separated from the monitored one. We discuss the modification to the kernel of the monitored machine to trace system call invocations, the definition of the legal traces and the checks to prove the trace is valid. We describe how PsycoTrace applies introspection to evaluate the assertions and analyze the state of the monitored machine and of its data structures. Finally, we present the security and performance results of the dynamic tools, and the implementation of the static tools. Sommario Il lavoro descrive PsycoTrace, uno strumento per la protezione da attacchi informatici basato su virtualizzazione. PsycoTrace fonde virtualizzazione ed introspezione per valutare asserzioni sullo stato di un processso in modo da rilevare attacchi che modifichino lo stato del processo. Inoltre, ad ogni processo viene associata una grammatica che descrive le tracce generate dall'esecuzione del processo. Una traccia definisce le invocazioni al sistema operativo del processo.
2009-04
Article
PeerReviewed
application/pdf
en
http://eprints.adm.unipi.it/610/1/psyco.pdf
Sgandurra, Daniele and Maggiari, Dario and Tamberi, Francesco and Baiardi, Fabrizio (2009) Transparent Process Monitoring in a Virtual Environment. Electronic Notes in Theoretical Computer Science, Volume (2). pp. 85-100.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B75H1-4VXW9BJ-7&_user=793840&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000043460&_version=1&_urlVersion=0&_userid=793840&md5=ff60aa330dbfef71866353f742ca56dc
doi:10.1016/j.entcs.2009.03.016
oai:eprints.adm.unipi.it:615
2010-12-20T10:50:40Z
7374617475733D696E7072657373
7375626A656374733D417265613031:494E462F3031
74797065733D61727469636C65
http://eprints.adm.unipi.it/615/
The wandering token: Congestion avoidance of a shared resource
Ciuffoletti, Augusto
INF/01 - Informatica
In a distributed system where scalability is an issue, the problem of enforcing mutual exclusion often arises in a soft form: the infrequent failure of the mutual exclusion predicate is tolerated, without compromising the consistent operation of the overall system. For instance this occurs when the operation subject to mutual exclusion requires massive use of a shared resource. We introduce a scalable soft mutual exclusion algorithm, based on previous termtokennext term passing: one distinguished feature of our algorithm is that instead of introducing an overlay topology we adopt a random walk approach. The consistency of our proposal is evaluated by simulation, and we exemplify its use in the coordination of large data transfers in a backbone based network. This algorithm is studied in the frame of the CoreGRID Institute of Grid Information, Resource and Workflow Monitoring Services, in cooperation with the FORTH Institute, in Greece.
2009
Article
PeerReviewed
application/pdf
it
http://eprints.adm.unipi.it/615/1/FGCS.pdf
Ciuffoletti, Augusto (2009) The wandering token: Congestion avoidance of a shared resource. Future Generation Computer Systems . ISSN 0167-739X (In Press)
http://www.sciencedirect.com/science/journal/0167739X
doi:10.1016/j.future.2009.05.002
oai:eprints.adm.unipi.it:623
2010-12-20T10:50:02Z
7374617475733D707562
7375626A656374733D417265613031:494E462F3031
74797065733D636F6E666572656E63655F6974656D
http://eprints.adm.unipi.it/623/
Collision avoidance for Delay_Req messages in broadcast media
Ciuffoletti, Augusto
INF/01 - Informatica
The time accuracy of the Precision Time Protocol deteriorates in consequence to Delay req/Delay resp session collisions common for applications using shared broadcast media. In this paper we propose a protocol that coordinates Delay_req/Delay_resp sessions with minimum changes to the original PTP protocol. Simulations illustrate protocol’s operation and demonstrate significant reduction of session collisions.
2009-10-12
Conference or Workshop Item
PeerReviewed
application/pdf
it
http://eprints.adm.unipi.it/623/1/paper.pdf
Ciuffoletti, Augusto (2009) Collision avoidance for Delay_Req messages in broadcast media. In: International IEEE Symposium on Precision Clock Synchronization, 12-16 ottobre 2009, Brescia, Italia.
oai:eprints.adm.unipi.it:624
2010-12-20T10:50:11Z
7374617475733D696E7072657373
7375626A656374733D417265613031:494E462F3031
7375626A656374733D417265613131:4D2D53544F2F3031
7375626A656374733D417265613130:4C2D414E542F3038
7375626A656374733D417265613131:4D2D4747522F3031
74797065733D626F6F6B5F73656374696F6E
http://eprints.adm.unipi.it/624/
Database, WebGIS, storia ed archeologia: riflessioni metodologiche dietro un progetto sulla Lunigiana medievale
Baldassarri, Monica
Mogorovich, Paolo
Salvatori, Enrica
INF/01 - Informatica
M-STO/01 - Storia medievale
L-ANT/08 - Archeologia cristiana e medievale
M-GGR/01 - Geografia
RIASSUNTO La relazione presenta il work in progress di un gruppo di ricerca formatosi di recente e composto da docenti, ricercatori e laureandi dell’Università di Pisa e del CNR. L’équipe ha come scopo la creazione di un WebGIS sulla Bassa Lunigiana medievale che possa risultare utile a diverse tipologie di utenti: l’amministratore, il turista e il singolo cittadino, il ricercatore. In particolare riguardo all’ultima tipologia di utente si è pensato a un sistema di informazione geografica che contenga dati sia storici che archeologici, in modo da ottenere nuove capacità di analisi fondate sull’incrocio di informazioni provenienti da ricerche diverse. L’elaborazione di tale prodotto ha messo in luce le difficoltà più acute che sorgono quando si cerca di porre in relazione in maniera automatizzata dati storici e archeologici al fine di conoscere il popolamento e l’insediamento di un territorio nel tempo. SUMMARY This paper presents the work in progress to create a WebGIS about Medioeval Bassa Lunigiana. The WebGIS can be useful by administrator, tourist, citizen and university researcher.
Università degli Studi di Siena
2009
Book Section
PeerReviewed
application/pdf
it
http://eprints.adm.unipi.it/624/1/testo_baldassarri.pdf
Baldassarri, Monica and Mogorovich, Paolo and Salvatori, Enrica (2009) Database, WebGIS, storia ed archeologia: riflessioni metodologiche dietro un progetto sulla Lunigiana medievale. In: Geografie del popolamento: casi di studio, metodi e teorie. Università degli Studi di Siena, Siena. (In Press)
ftp://192.167.118.102/testo_baldassarri.pdf
oai:eprints.adm.unipi.it:626
2010-12-20T10:49:38Z
7374617475733D707562
7375626A656374733D417265613031:494E462F3031
7375626A656374733D417265613131:4D2D53544F2F3034
7375626A656374733D417265613131:4D2D5045442F3031
74797065733D61727469636C65
http://eprints.adm.unipi.it/626/
Hardcore history: ovvero la storia in podcast. Analisi del podcasting dedicato ad argomenti storici in lingua inglese, francese, italiana e spagnola
Salvatori, Enrica
INF/01 - Informatica
M-STO/04 - Storia contemporanea
M-PED/01 - Pedagogia generale e sociale
RIASSUNTO Analisi del fenomeno del podcasting di argomento storico a scopo divulgativo e didattico. SUMMARY Analysis of podcasting about history from the point of view of education and popularization
2009
Article
PeerReviewed
application/pdf
it
http://eprints.adm.unipi.it/626/1/testopodcast.pdf
Salvatori, Enrica (2009) Hardcore history: ovvero la storia in podcast. Analisi del podcasting dedicato ad argomenti storici in lingua inglese, francese, italiana e spagnola. Memoria e Ricerca, 30/200 (1). pp. 171-187. ISSN 1127-0195
http://www.fondazionecasadioriani.it/modules.php?name=MR&op=abstract&id=481
oai:eprints.adm.unipi.it:644
2010-12-20T10:49:31Z
7374617475733D707562
7375626A656374733D417265613031:494E462F3031
74797065733D61727469636C65
http://eprints.adm.unipi.it/644/
Masking Patterns in Sequences: A New Class of Motif Discovery with Don't Cares
Battaglia, Giovanni
Grossi, Roberto
Cangelosi, Davide
Pisanti, Nadia
INF/01 - Informatica
SUMMARY We introduce a new notion of motifs, called masks, that succinctly represents the repeated patterns for an input sequence T of n symbols drawn from an alphabet. We show how to build the set of all frequent maximal masks of length L in O.2Ln/ time and space in the worst case, using the KarpMillerRosenberg approach. We analytically show that our algorithm performs better than the method based on constant-time enumerating and checking all the potential .jj C 1/L candidate patterns in T , after a polynomial-time preprocessing of T . Our algorithm is also cache-friendly, attaining O.2L sort.n// block transfers, where sort.n/ is the cache complexity of sorting n items.
2009
Article
PeerReviewed
application/pdf
it
http://eprints.adm.unipi.it/644/1/Final_version_Battaglia_Cangelosi_Grossi_Pisanti.pdf
Battaglia, Giovanni and Grossi, Roberto and Cangelosi, Davide and Pisanti, Nadia (2009) Masking Patterns in Sequences: A New Class of Motif Discovery with Don't Cares. Theoretical Computer Science, 410 (43). pp. 4327-4340. ISSN 0304-3975
http://www.sciencedirect.com/science/journal/03043975
doi:10.1016/j.tcs.2009.07.014
oai:eprints.adm.unipi.it:645
2010-12-20T10:49:29Z
7374617475733D707562
7375626A656374733D417265613031:494E462F3031
74797065733D61727469636C65
http://eprints.adm.unipi.it/645/
Suffix tree characterization of maximal motifs in biological sequences
Federico, Maria
Pisanti, Nadia
INF/01 - Informatica
SUMMARY: Finding motifs in biological sequences is one of the most intriguing problems for string algorithm designers due to, on the one hand, the numerous applications of this problem in molecular biology and, on the other hand, the challenging aspects of the computational problem. Indeed, when dealing with biological sequences it is necessary to work with approximations (that is, to identify fragments that are not necessarily identical, but just similar, according to a given similarity notion), and this complicates the problem. Existing algorithms run in time linear with respect to the input size. Nevertheless, the output size can be very large due to the approximation (namely exponential in the approximation degree). This often makes the output unreadable, as well as slowing down the inference itself. A high degree of redundancy has been detected in the set of motifs that satisfy traditional requirements, even for exact motifs. Moreover, it has been observed many times that only a subset of these motifs, namely the maximal motifs, could be enough to provide the information of all of them. In this paper, we aim at removing such redundancy. We extend some notions of maximality already defined for exact motifs to the case of approximate motifs with Hamming distance, and we give a characterization of maximal motifs on the suffix tree. Given that this data structure is used by a whole class of motif extraction tools, we show how these tools can be modified to include the maximality requirement without changing the asymptotical complexity.
2009
Article
PeerReviewed
application/pdf
it
http://eprints.adm.unipi.it/645/1/suffix.pdf
Federico, Maria and Pisanti, Nadia (2009) Suffix tree characterization of maximal motifs in biological sequences. Theoretical Computer Science, 410 (43). pp. 4391-4410. ISSN 0304-3975
http://www.sciencedirect.com/science/journal/03043975
doi:10.1016/j.tcs.2009.07.020
oai:eprints.adm.unipi.it:649
2010-12-20T10:49:18Z
7374617475733D707562
7375626A656374733D417265613031:494E462F3031
7375626A656374733D417265613039:494E472D494E462F3035
74797065733D626F6F6B5F73656374696F6E
http://eprints.adm.unipi.it/649/
Estimating The Size Of Peer-To-Peer Networks Using Lambert’s W Function
Ciuffoletti, Augusto
Bustos-Jimenez, Javier
Bersano, Nicolas
Schaeffer, Satu Elisa
Piquer, Jose Miguel
Iosup , Alexandru
INF/01 - Informatica
ING-INF/05 - Sistemi di elaborazione delle informazioni
SUMMARY In this work, we address the problem of locally estimating the size of a Peer-to-Peer (P2P) network using local information. We present a novel approach for estimating the size of a peer-to-peer (P2P) network, fitting the sum of new neighbors discovered at each iteration of a breadth-first search (BFS) with a logarithmic function, and then using Lambert’s W function to solve a root of a ln(n) + b − n = 0, where n is the network size. With rather little computation, we reach an estimation error of at most 10 percent, only allowing the BFS to iterate to the third level.
Springer
Gorlatch, Sergei
Fragopoulou, Paraskevi
Priol, Thierry
2008
Book Section
PeerReviewed
application/pdf
en
http://eprints.adm.unipi.it/649/1/estimate.pdf
Ciuffoletti, Augusto and Bustos-Jimenez, Javier and Bersano, Nicolas and Schaeffer, Satu Elisa and Piquer, Jose Miguel and Iosup , Alexandru (2008) Estimating The Size Of Peer-To-Peer Networks Using Lambert’s W Function. In: Grid Computing - Achievements and Prospects. Springer, pp. 61-72. ISBN 978-0-387-09456-4
http://www.springer.com/computer/communications/book/978-0-387-09456-4
oai:eprints.adm.unipi.it:655
2010-12-20T10:48:53Z
7374617475733D707562
7375626A656374733D417265613031:494E462F3031
74797065733D626F6F6B5F73656374696F6E
http://eprints.adm.unipi.it/655/
Scalable concurrency control in a dynamic membership
Ciuffoletti, Augusto
Asim, Ali
INF/01 - Informatica
SUMMARY We introduce a solution for a concurrency control problem which is frequently encountered in practice: in a dynamic system we want that the load on a centralized resource is uniformly distributed among users, offering a predictable performance as long as it is not overloaded. We propose an original solution based on probabilistic assumptions, and we comment early experimental results.
Springer
Meyer, Norbert
Talia, Domenico
Yahyapour, Ramin
2009
Book Section
PeerReviewed
application/pdf
en
http://eprints.adm.unipi.it/655/1/cur_2008_e.pdf
Ciuffoletti, Augusto and Asim, Ali (2009) Scalable concurrency control in a dynamic membership. In: Grid and Services Evolution. Springer, pp. 205-214. ISBN 978-0-387-85965-1
http://www.springer.com/computer/communications/book/978-0-387-85965-1
10.1007/978-0-387-85966-8
oai:eprints.adm.unipi.it:657
2010-12-20T10:48:22Z
7374617475733D707562
7375626A656374733D417265613031:494E462F3031
74797065733D626F6F6B5F73656374696F6E
http://eprints.adm.unipi.it/657/
Architecture of a Network Monitoring Element
Ciuffoletti, Augusto
Polychronakis, Michalis
INF/01 - Informatica
SUMMARY A Network Monitoring system is a vital component of a Grid; however, its scalability is a challenge. We propose a network monitoring approach that combines passive monitoring, a domain oriented overlay network, and an attitude for demand driven monitoring sessions. In order to keep into account the demand for extreme scalability, we introduce a solution for two problems that are inherent to the proposed approach: security and group membership maintenance.
Springer
Lehner, Wolfgang
Meyer, Norbert
Streit, Achim
Stewart, Craig
2007
Book Section
PeerReviewed
application/pdf
en
http://eprints.adm.unipi.it/657/1/cur_2006_e.pdf
Ciuffoletti, Augusto and Polychronakis, Michalis (2007) Architecture of a Network Monitoring Element. In: Euro-Par 2006 Workshops: Parallel Processing - Selected papers. Springer, pp. 5-14. ISBN 978-3-540-72226-7
10.1007/978-3-540-72337-0
oai:eprints.adm.unipi.it:669
2010-12-20T10:48:15Z
7374617475733D707562
7375626A656374733D417265613031:494E462F3031
7375626A656374733D417265613039:494E472D494E462F3035
74797065733D61727469636C65
http://eprints.adm.unipi.it/669/
Partial model checking via abstract interpretation
De Francesco, Nicoletta
Lettieri, Giuseppe
Vaglini, Gigliola
Martini, Luca
INF/01 - Informatica
ING-INF/05 - Sistemi di elaborazione delle informazioni
SUMMARY Nowadays the emphasis in software engineering research is on the evolution of pre-existing sub-systems and component development. In this context, we tackle the following problem: given the formal specification of the system P, already built, how to characterize possible collaborators of P, through a given communication interface L, to the satisfaction of a given property φ. We propose an abstract interpretation framework to reason about this problem in a systematic way. Given P and L, the set of all transition systems that, composed with P and restricted by L, satisfy φ, is modeled as the abstract semantics of φ, parametric with respect to P and L. We show that the algorithm developed by Andersen (1995) [1] can be formulated in our framework.
2010-01-01
Article
PeerReviewed
application/pdf
it
http://eprints.adm.unipi.it/669/1/ccs.pdf
De Francesco, Nicoletta and Lettieri, Giuseppe and Vaglini, Gigliola and Martini, Luca (2010) Partial model checking via abstract interpretation. Information Processing Letters, 110 (3). pp. 99-103. ISSN 0020-0190
http://www.sciencedirect.com/science/journal/00200190
doi:10.1016/j.ipl.2009.10.014
oai:eprints.adm.unipi.it:702
2010-12-20T10:38:56Z
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http://eprints.adm.unipi.it/702/
Integrated library services within the web 2.0 context: from the development of tools for e-learning to open access repositories
Lùperi, Patrizia
Gullà, Valentina
M-PED/03 - Didattica e pedagogia speciale
INF/01 - Informatica
M-STO/08 - Archivistica, bibliografia e biblioteconomia
Nella relazione verranno presentate le principali innovazioni introdotte dalle tecnologie e dagli strumenti del web 2.0 nei servizi bibliotecari. Saranno inoltre presi in considerazione alcuni repository italiani di risorse didattiche ed educative che verranno confrontati con altre esperienze europee ed internazionali. Concluderemo ipotizzando soluzioni operative sia a medio che lungo termine in ambito nazionale, per una più efficace standardizzazione e diffusione di learning object e di contenuti destinati ad archivi digitali. The present paper is directed to show, on one hand, the contribution given by Information and Communication Technologies (ICT) to teaching and learning activities that currently take place in various contexts; on the other hand it refers to other ongoing projects about the ways to archive and share educational resources. Our attention will focus on: •the importance of networking technologies for learning and for the management and dissemination of information and knowledge •the creation of innovative learning tools •the importance that is going to be taken by non-formal educational settings (such as libraries) in lifelong learning society •towards which direction it’s important to work to ensure that information sources are actually available to every active citizen.
2010-03
Conference or Workshop Item
NonPeerReviewed
application/pdf
it
http://eprints.adm.unipi.it/702/1/interv_eng_definitivo.rtf
Lùperi, Patrizia and Gullà, Valentina (2010) Integrated library services within the web 2.0 context: from the development of tools for e-learning to open access repositories. In: International Tecnology, Education and Development Conference, INTED 2010, 8-10 marzo 2010, Valencia, Spagna.
http://www.iated.org/inted2010/
oai:eprints.adm.unipi.it:712
2010-12-20T10:46:45Z
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7375626A656374733D417265613031:494E462F3031
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74797065733D636F6E666572656E63655F6974656D
http://eprints.adm.unipi.it/712/
La trasmissione della memoria da Guccini ad Avatar: un ritorno al futuro
Salvatori, Enrica
M-PED/03 - Didattica e pedagogia speciale
INF/01 - Informatica
M-STO/04 - Storia contemporanea
RIASSUNTO Contributo nell'ambito della Storia Digitale e delle nuove tecnologie per ricordare il passato e preservare la memoria del presente. Si tratta di un ragionamento sull'evoluzione dei modi di apprendimento del passato partendo dalla rottura della trasmissione orale tra generazioni (il vecchio e il bambino di Guccini come spunto di partenza) all'esperienza del marine protagonista di Avatar, che “apprende” la memoria di un popolo in maniera immersiva virtuale. Il passaggio è segnato dagli strumenti che attualmente sono considerati all'avanguardia nel processo di apprendimento del passato e che implicano un uso consapevole delle nuove tecnologie, dal videopodcasting agli ambienti virtuali multiutente come Second Life. Una proiezione nel futuro di quanto sta avvenendo farebbe ipotizzare un ritorno a un sistema di ricezione della memoria per alcuni aspetti simile a quello usato al tempo dei nonni e bisnonni. Un ritorno al futuro. SUMMARY Lecture on the Digital History and teh new technologies helping to remember the past and preserve the memory. The lecture is about the evolution of learning methodology starting from the failure of oral transmission between generations (the old man and the child in a Guccini's song) to the experience of the marine character in Avatar movie, who "learns" the memory of a people in an immersive virtual environment. The transition is marked by tools now considered at the forefront of learning techinques and involves a conscious use of new technologies: from videopodcasting to GIS, from video to multiuser virtual environments as Second Life. An hypothetical projection of what is happening would suggest a return to a learning system similar to that was used in the time of our grandparents and great grandparents. Back to the future.
2010
Conference or Workshop Item
PeerReviewed
application/pdf
it
http://eprints.adm.unipi.it/712/1/SalvatoriRelazione.pdf
Salvatori, Enrica (2010) La trasmissione della memoria da Guccini ad Avatar: un ritorno al futuro. In: 2060: WHAT WILL BE THE SOURCES FOR THE HISTORY OF OUR TIMES? A coming together of techniques, practices and the social sciences, 8-9 aprile 2010, Torino, Italia. (In Press)
http://www.fondazionetelecomitalia.it/doc/programma.pdf
oai:eprints.adm.unipi.it:724
2010-12-20T10:45:51Z
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http://eprints.adm.unipi.it/724/
The wandering token: Congestion avoidance of a shared resource
Ciuffoletti, Augusto
INF/01 - Informatica
In a distributed system where scalability is an issue, the problem of enforcing mutual exclusion often arises in a soft form: the infrequent failure of the mutual exclusion predicate is tolerated, without compromising the consistent operation of the overall system. For instance this occurs when the operation subject to mutual exclusion requires massive use of a shared resource. We introduce a scalable soft mutual exclusion algorithm, based on previous termtokennext term passing: one distinguished feature of our algorithm is that instead of introducing an overlay topology we adopt a random walk approach. The consistency of our proposal is evaluated by simulation, and we exemplify its use in the coordination of large data transfers in a backbone based network. This algorithm is studied in the frame of the CoreGRID Institute of Grid Information, Resource and Workflow Monitoring Services, in cooperation with the FORTH Institute, in Greece.
2010
Article
PeerReviewed
application/pdf
en
http://eprints.adm.unipi.it/724/1/paper.pdf
Ciuffoletti, Augusto (2010) The wandering token: Congestion avoidance of a shared resource. Future Generation Computer Systems, 2010 (26). pp. 473-478. ISSN 0167-739X
http://www.sciencedirect.com/science/journal/0167739X
doi:10.1016/j.future.2009.05.002
oai:eprints.adm.unipi.it:1219
2011-05-03T13:37:59Z
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7375626A656374733D417265613031:494E462F3031
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http://eprints.adm.unipi.it/1219/
Learning by Building in SL: A Reflection on an Interdisciplinary and International Experience
Denard, Hugh
Salvatori, Enrica
Simi, Maria
ICAR/17 - Disegno
INF/01 - Informatica
M-STO/01 - Storia medievale
M-STO/02 - Storia moderna
M-STO/04 - Storia contemporanea
This chapter will report on, and critically assess the outcome of a two year-long experimental educational
project using Second Life (SL) as a teaching and learning platform. The project’s main goal was to
investigate the added value of a multi-user environment in a multi-disciplinary and international context
for learning about history, archaeology, acquiring a scientific approach and methodology to historical
reconstruction and 3D visualization, as well as the skills to use different media technologies for communication
and collaboration. This chapter will describe educational facilities and resources as well
as heritage visualization projects built in the Digital Humanities Island in SL, where the collaboration
between King’s College London and the University of Pisa took place.
IGI Global
Braman, James
Vincenti, Giovanni
2011
Book Section
PeerReviewed
application/pdf
en
cc_by_nc
http://eprints.adm.unipi.it/1219/1/LearningbyBuilding.pdf
Denard, Hugh and Salvatori, Enrica and Simi, Maria (2011) Learning by Building in SL: A Reflection on an Interdisciplinary and International Experience. In: Multi-User Virtual Environments for the Classroom: Practical Approaches to Teaching in Virtual Worlds. IGI Global, Hershey PA, pp. 134-158. ISBN 978-1-60960-545-2
oai:eprints.adm.unipi.it:1235
2011-10-13T07:43:17Z
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http://eprints.adm.unipi.it/1235/
Implementing a probabilistic clock synchronization algorithm
Ciuffoletti, Augusto
Alari, Gianluigi
INF/01 - Informatica
ING-INF/03 - Telecomunicazioni
SUMMARY In this paper we present a new probabilistic clock synchronization algorithm, its prototype implementation and experimental results. The algorithm follows the client-server programming paradigm and is designed to work in a departmental environment with few servers and a number of clients connected through an arbitrary network topology.
At the core of the algorithm is a remote clock reading method that mitigates the negative effects of message delay uncertainty. The implementation proves the effectiveness of this approach and corroborates the theoretical speculations.
Springer Verlag
1997
Article
PeerReviewed
application/pdf
en
http://eprints.adm.unipi.it/1235/1/cur_1996_b.pdf
Ciuffoletti, Augusto and Alari, Gianluigi (1997) Implementing a probabilistic clock synchronization algorithm. Real-Time Systems, 13 (1). pp. 25-46. ISSN 0922-6443
http://www.springerlink.com/content/rq53804787561381/
DOI: 10.1023/A:1007900902186
oai:eprints.adm.unipi.it:1248
2015-11-05T10:22:51Z
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http://eprints.adm.unipi.it/1248/
Optimizing bulk data transfers using network
measurements: a practical case
Augusto, Ciuffoletti
Merola, L.
Palmieri, F.
Pardi, Silvio
Russo, G.
INF/01 - Informatica
ING-INF/05 - Sistemi di elaborazione delle informazioni
SUMMARY The quality of the connectivity provided by the network infrastructure of a Grid is a crucial factor to guarantee the accessibility of Grid services, schedulate efficiently processing and data transfer activity on the Grid and meet QoS expectations. Yet most Grid application do not take into consideration the expected performance of the network resources they plan to use. In this paper we describe the effective use of a Grid Monitoring framework, whose measurements are used to introduce network aware features in a legacy application.
We use GlueDomains, a network monitoring framework oriented to Grid infrastructures that measures a small (although possibly extensible) set of network parameters. Such framework works off the shelf with minimal administrative effort, is reliable, and has a negligible impact on
system operation. The deployment covers a Metropolitan Grid infrastructure, aimed at supporting a data intensive eScience application. We describe a real use case consisting of bulk data trasfers during the operation of the Grid for the Virgo experiment.
IOP Publishing
2010
Article
NonPeerReviewed
application/pdf
en
http://eprints.adm.unipi.it/1248/1/paper_network.pdf
Augusto, Ciuffoletti and Merola, L. and Palmieri, F. and Pardi, Silvio and Russo, G. (2010) Optimizing bulk data transfers using network measurements: a practical case. Journal of Physics - Conference series, 219 (6). ISSN 1742-6588
http://iopscience.iop.org/1742-6596/219/6/062063/pdf/1742-6596_219_6_062063.pdf
10.1088/1742-6596/219/6/062063
oai:eprints.adm.unipi.it:1913
2014-04-24T08:14:44Z
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http://eprints.adm.unipi.it/1913/
A simple and generic interface for a Cloud Monitoring System
Ciuffoletti, Augusto
INF/01 - Informatica
ING-INF/05 - Sistemi di elaborazione delle informazioni
The paper addresses the definition of an ontology for cloud monitoring activities, with the aim of defining a
standard interface for their configuration. To be widely adopted, such ontology must be extremely flexible,
coping with a wide range of use cases: from the minimalist plug-and-play user, to the one governing a complex
infrastructure.
Our work is based on the Open Cloud Computing Interface, that is an open, community driven OGF standard
allowing boundary-level interfaces to be built using RESTful patterns over HTTP. Among others, OpenStack
and OpenNebula adopt OCCI.
Using the OCCI ontology we define two kinds that are associated with the basic components of a monitoring
infrastructure: the collector link, that performs measurements, and the sensor resource, that aggregates data
and undertakes actions.
This paper is a compact and self-contained revision of a document currently under discussion inside the OCCI
community.
2014-04-04
Conference or Workshop Item
PeerReviewed
application/pdf
en
cc_by_nd
http://eprints.adm.unipi.it/1913/1/paper.pdf
Ciuffoletti, Augusto (2014) A simple and generic interface for a Cloud Monitoring System. In: CLOSER 2014 - 4th International Conference on Cloud Computing and Services Science, April 2-5 2014, Barcelona.
oai:eprints.adm.unipi.it:1921
2014-10-13T08:26:34Z
oai:eprints.adm.unipi.it:1922
2015-01-26T07:42:04Z
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Dynamical Neural Networks Construction for Processing of Labeled Structures
Sperduti, Alessandro
Starita, Antonina
INF/01 - Informatica
We show how Labeling RAAM (LRAAM) can be exploited to generate
`on the fly' neural networks for associative access of labeled structures.
The topology of these networks, that we call Generalized Hopfield
Networks (GHN), depends on the topology of the query used
to retrieve information, and the weights on the networks' connections are
the weights of the LRAAM encoding the structures.
A method for incremental discovering of multiple solutions to a given
query is presented. This method is based on terminal repellers,
which are used to `delete' known solutions from the set of
admissible solutions to a query. Terminal repellers are also used
to implement exceptions at query level, i.e., when a solution to a
query must satisfy some negative constraints on the labels and/or
substructures.
Besides, the proposed model solves very naturally the connectionist variable
binding problem at query level.
Some results for a tree-like query are presented.
Finally, we define a parallel mode of execution, exploiting
terminal repellers, for the GHN, and we propose to use
terminal attractors for implementing
shared variables and graph queries.
Università di Pisa
1995-01-01
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1922/1/TR-95-01.ps.gz
Sperduti, Alessandro and Starita, Antonina (1995) Dynamical Neural Networks Construction for Processing of Labeled Structures. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-95-01.ps.gz
oai:eprints.adm.unipi.it:1923
2014-12-10T09:08:32Z
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On the implementation of the MAP paradigm on a 2D-mesh
Bacci, Bruno
Pelagatti, Susanna
INF/01 - Informatica
Parallelism, Optimal Data Distribution/Collection, P3L This document describes
the MAP paradigm of parallelism and the problems related to its e cient imple-
mentation on a 2D-mesh. In particular, we rst discuss how parallel algorithms ex-
ploiting MAP parallelism can be easily expressed by using the P3L Map construct.
Then, we discuss an implementation template for a massively parallel architecture
with a 2D-mesh topology and Transputer-like processing nodes. The template is
asymptotically optimal with respect to the strategies embedded for data distribu-
tion, data collection and process allocation
Università di Pisa
1995-02-05
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1923/1/TR-95-03.ps.gz
Bacci, Bruno and Pelagatti, Susanna (1995) On the implementation of the MAP paradigm on a 2D-mesh. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-95-03.ps.gz
oai:eprints.adm.unipi.it:1924
2015-01-26T07:43:00Z
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http://eprints.adm.unipi.it/1924/
Elimination of Conditions
Viry, Patrick
INF/01 - Informatica
We present a transformation from any conditional rewrite systems into
non conditional ones and prove its correctness. The transformed systems
are quite intuitive and well suited for parallel execution. We also
show how termination and confluence of the original system are preserved
in the transformed one.
Università di Pisa
1995-12-01
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1924/1/TR-95-19.ps.gz
Viry, Patrick (1995) Elimination of Conditions. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-95-19.ps.gz
oai:eprints.adm.unipi.it:1925
2015-01-26T07:42:54Z
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http://eprints.adm.unipi.it/1925/
Rewriting modulo a rewrite system
Viry, Patrick
INF/01 - Informatica
We introduce rewriting with two sets of rules, the first interpreted
equationally and the second not. A
semantic view considers equational rules as defining an equational theory
and reduction rules as defining
a rewrite relation modulo this theory. An operational view considers both
sets of rules as similar. We
introduce sufficient properties for these two views to be equivalent (up to
different notions of
equivalence). The paper ends with a collection of example showing the
effectiveness of this approach.
Università di Pisa
1995-12-01
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1925/1/TR-95-20.ps.gz
Viry, Patrick (1995) Rewriting modulo a rewrite system. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-95-20.ps.gz
oai:eprints.adm.unipi.it:1926
2015-01-26T07:42:47Z
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http://eprints.adm.unipi.it/1926/
Solving Semidefinite Quadratic Problems Within Nonsmooth Optimization Algorithms
Frangioni, Antonio
INF/01 - Informatica
Bundle methods for Nondifferentiable Optimization are widely
recognised as one of the best choices for the solution of Lagrangean
Duals; one of their major drawbacks is that they require the solution
of a Semidefinite Quadratic Programming subproblem at every
iteration. We present an active-set method for the solution of such
problems, that enhances upon the ones in the literature by
distinguishing among bases with different properties and exploiting
their structure in order to reduce the computational cost of the basic
step. Furthermore, we show how the algorithm can be adapted to the
several needs that arises in practice within Bundle algorithms; we
describe how it is possible to allow constraints on the primal
direction, how special (box) constraints can be more efficiently dealt
with and how to accommodate changes in the number of variables of the
nondifferentiable function. Finally, we describe the important
implementation issues, and we report some computational experience to
show that the algorithm is competitive with other QP codes
when used within a Bundle code for the solution of Lagrangean Duals of
large-scale (Integer) Linear Programs.
Università di Pisa
1995-05-01
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1926/1/TR-95-10.ps.gz
Frangioni, Antonio (1995) Solving Semidefinite Quadratic Problems Within Nonsmooth Optimization Algorithms. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-95-10.ps.gz
oai:eprints.adm.unipi.it:1927
2015-01-26T07:42:39Z
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Latency and Bandwidth Requirements of Massively Parallel Programs: FFT as a Case Study
Petrini, Fabrizio
Vanneschi, Marco
INF/01 - Informatica
Many theoretical models of parallel computation are based on overly
simplistic assumptions on the performance of the interconnection
network. For example they assume constant latency for any
communication pattern or infinite bandwidth. This paper presents a
case study based on the FFT transpose algorithm, which is mapped on
two families of scalable interconnection networks, the k-ary
n-trees and the k-ary n-cubes. We analyze in depth the network
behavior of a minimal adaptive algorithm for the k-ary n-trees
and three algorithms for the k-ary n-cubes, each offering an
increasing degree of adaptivity: the deterministic routing, a
minimal adaptive routing based on Duato's methodology and the Chaos
routing, a non-minimal adaptive cut-through version of the hot
potato routing. The simulation results collected on topologies with
up to 256 processing nodes show that the k-ary n-trees can
efficiently support the basic FFT algorithm by factoring the
personalized broadcast in a sequence of congestion-free steps.
Though k-ary n-cubes are less favored in terms of bisection
bandwidth, we can narrow the performance gap between the two
interconnection networks by properly interleaving communication and
computation. While in the presence of bandwidth-bound patterns the
communication latency becomes difficult to predict, the global
accepted network bandwidth converges to a fixed value after a
stabilization period, though both adaptive algorithms on the cubes
suffer from post-saturation problems.
Università di Pisa
1996-03-07
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1927/1/TR-96-02.ps.gz
Petrini, Fabrizio and Vanneschi, Marco (1996) Latency and Bandwidth Requirements of Massively Parallel Programs: FFT as a Case Study. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-02.ps.gz
oai:eprints.adm.unipi.it:1928
2015-01-26T07:42:33Z
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http://eprints.adm.unipi.it/1928/
Flows on hypergraphs
Cambini, Riccardo
Gallo, Giorgio
Scutellà, Maria Grazia
INF/01 - Informatica
We consider the capacitated minimum cost flow problem on directed
hypergraphs. We define spanning hypertrees so generalizing the spanning
tree of a standard graph, and show that, like in the standard and in the
generalized minimum cost flow problems, a correspondence exists between
bases and spanning hypertrees. Then, we show that, like for the
network simplex algorithms for the standard and for the generalized
minimum cost flow problems, most of the computations performed at each
pivot operation have direct hypergraph interpretations.
Università di Pisa
1996-03-08
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1928/1/TR-96-04.ps.gz
Cambini, Riccardo and Gallo, Giorgio and Scutellà, Maria Grazia (1996) Flows on hypergraphs. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-04.ps.gz
oai:eprints.adm.unipi.it:1929
2015-01-26T07:42:21Z
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A Logic Abstract Machine for Active Object-Oriented Databases
Carboni, Marilisa
Giannotti, Fosca
Manco, Giuseppe
Pedreschi, Dino
INF/01 - Informatica
We show how a fragment of the logical data language LDL++
can be used to define an abstract machine supporting the
essence of active/deductive object-oriented databases.
We exhibit a compilation into the mentioned logic
language of the basic features of the object model,
including the schema definition language, the query language
with multiple roles, the basic update operations, and a
form of active rules.
The target logic language, which is essentially Datalog
extended with non-determinism and a form of stratified
negation, has been chosen with a twofold aim.
On one side, it should provide an abstract implementation level,
where the object model is declaratively reconstructed
and its semantics clarified.
On the other side, the proposed compilation should form
the basis of a realistic implementation, as LDL++ can be
efficiently executed, and supports real side effects.
Università di Pisa
1996-02-26
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1929/1/TR-96-05.ps.gz
Carboni, Marilisa and Giannotti, Fosca and Manco, Giuseppe and Pedreschi, Dino (1996) A Logic Abstract Machine for Active Object-Oriented Databases. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-05.ps.gz
oai:eprints.adm.unipi.it:1930
2015-01-26T07:42:10Z
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L'Ambiente di Programmazione P3L nel sistema di supporto PVM su Rete di Calcolatori Eterogenei
Bacci, Bruno
Cantalupo, Barbara
Guerrini, Nicola
Pelagatti, Susanna
INF/01 - Informatica
In this document, we discuss a prototype compiler of P3L, which is a
structured parallel programming language, on a network of
heterogeneous workstations. P3L is implemented on top of the abstract
parallel machine provided by PVM. In particular, we discuss the
definition of a new set of implementation templates, which are
designed in order to meet the target features, and we show how the
correct configurations for the abstract machine can be automatically
generated within the support.
(The document is written in Italian.)
Università di Pisa
1995-10-01
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1930/1/TR-95-14.ps.gz
Bacci, Bruno and Cantalupo, Barbara and Guerrini, Nicola and Pelagatti, Susanna (1995) L'Ambiente di Programmazione P3L nel sistema di supporto PVM su Rete di Calcolatori Eterogenei. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-95-14.ps.gz
oai:eprints.adm.unipi.it:1931
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A Bundle type Dual-ascent Approach to Linear Multi-Commodity Min Cost Flow Problems
Frangioni, Antonio
Gallo, Giorgio
INF/01 - Informatica
We present a cost decomposition approach to Linear Multicommodity Min Cost
Flow problems, based on dualizing the mutual capacity constraints: the
resulting Lagrangean Dual is solved by means of a new, specialized Bundle
type-dual ascent algorithm. Although decomposition approaches are generally
believed not to be competitive, even for the solution of large-scale
network structured problems, we present evidence based on extensive
computational comparisons that a careful implementation of a decomposition
algorithm can outperform several other approaches, especially on problems
where the number of commodities is "large" w.r.t. the size of the graph.
Our specialized Bundle algorithm is characterised by a new heuristic for
the trust region parameter handling, and embeds a custom, fast Quadratic
Programming solver that permits the implementation of a Lagrangean
variables generation strategy. The Lagrangean Relaxation solver is capable
of exploiting the structural properties of the single-commodity Min Cost
Flow subproblems to avoid using a "generic" MCF solver whenever it is
possible. The proposed approach can be easily extended to handle extra
constraints or variants such as the Nonsimultaneous Multicommodity problem.
In our computational experience, we also studied the impact on the relative
efficiencies of the different approaches tested of some characteristics,
such as the number of commodities w.r.t. the total size of the problem.
Università di Pisa
1996-12-15
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1931/1/TR-96-01.ps.gz
Frangioni, Antonio and Gallo, Giorgio (1996) A Bundle type Dual-ascent Approach to Linear Multi-Commodity Min Cost Flow Problems. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-01.ps.gz
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Introducing Spacial Graphs (updated version)
Luccio, Fabrizio
Pagli, Linda
INF/01 - Informatica
We introduce spatial graphs through a natural extension of the
concept of planarity in three dimensions.
For a graph G=(V,E), a face is a simple cycle of edges, and
a complete set of faces is such that each edge belonging to a cycle in
E is on at least one face in the set. G is spatial if admits a
three-dimensional representation R with a complete set of faces
consisting of simple surfaces, such that no two faces intersect
except along the common edge. In particular G is called k-spatial
if R includes k cells (spatial regions); and is called plane-face
spatial if all the faces in R are plane.
We prove that all graphs are 1-spatial, but not all of them are
(k>1)-spatial or plane-face spatial. In particular, $K_n$ is
$(n^2-3n)/2$-spatial and plane-face spatial. We derive some basic
properties of spatial graphs as natural three-dimensional extensions
of the properties of planar graphs.
Università di Pisa
1995-04-01
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1932/1/TR-95-08.ps.gz
Luccio, Fabrizio and Pagli, Linda (1995) Introducing Spacial Graphs (updated version). Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-95-08.ps.gz
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Applying Bundle Methods to the Optimization of Polyhedral Functions: An Applications-Oriented Development
Carraresi, Paolo
Frangioni, Antonio
Nonato, Maddalena
INF/01 - Informatica
Among practical methods for large-scale for Nondifferentiable
Optimization (NDO), Bundle methods are widely recognized to play a
relevant role; despite their potential, however, they are not often
utilized for maximization of polyhedral functions, that appears in
many different context such as Lagrangean Duals and decomposition
algorithms, since simpler-to-program but less efficient approaches
like subgradient methods are preferred. The aim of this work is to
provide an applications-oriented survey of the theory of Bundle
methods when applied to problems arising in continuous and
combinatorial optimization, with an introduction to the several
variants of Bundle approaches that can be built up by using a limited
set of basic concepts and tools.
Università di Pisa
1995-12-01
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1933/1/TR-95-17.ps.gz
Carraresi, Paolo and Frangioni, Antonio and Nonato, Maddalena (1995) Applying Bundle Methods to the Optimization of Polyhedral Functions: An Applications-Oriented Development. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-95-17.ps.gz
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K-ary N-trees: High Performance Networks for Massively Parallel Architectures
Petrini, Fabrizio
Vanneschi, Marco
INF/01 - Informatica
The past few years have seen a rise in popularity of massively
parallel architectures that use fat-trees as their interconnection
In this paper we formalize a parametric family of
fat-trees, the k-ary n-trees, built with constant arity switches
interconnected in a regular topology. A simple adaptive routing
algorithm for k-ary n-trees sends each message to one of the
nearest common ancestors (NCA) of both source and
destination choosing the less loaded physical channels and then
reaches the destination following the unique available path. Through
simulation on a 4-ary 4-tree with 256 nodes, we analyze some
variants of the adaptive algorithm that utilize wormhole routing
with 1, 2 and 4 virtual channels. The experimental results
show that the uniform, bit reversal and transpose traffic patterns
are very sensitive to the flow control strategy. In all these cases,
the saturation points are between 35-40% of the network
capacity with 1 virtual channel, 55-60% with 2 virtual
channels and around 75% with 4 virtual channels and after
saturation, the network throughput remains stable. Increasing the
number of virtual channels slightly worsens the average network
latency, but improves the bounds on the distribution. The
complement traffic, a representative of the class of the
congestion-free communication patterns, reaches an optimal
performance, with a saturation point at 97% of the capacity for
all flow control strategies. In this case virtual channels are of
little help and the average network latency experiences an increase
proportional to the number of virtual channels, due to the
multiplexing of several packets onto the same physical path.
Università di Pisa
1995-12-15
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1934/1/TR-95-18.ps.gz
Petrini, Fabrizio and Vanneschi, Marco (1995) K-ary N-trees: High Performance Networks for Massively Parallel Architectures. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-95-18.ps.gz
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Dual Algorithms for the Shortest Path Tree Problem
Pallottino, Stefano
Scutellà, Maria Grazia
INF/01 - Informatica
We consider dual approaches for the Shortest Path Tree Problem. After a
brief
introduction to the problem, we review the most important dual algorithms
which have been described in the literature for its solution, and propose
a new family of dual ascent algorithms. In these algorithms, "local" and
"global" dual updating operations are performed at the nodes in order to
enlarge a partial shortest path tree, which at the beginning contains only
the root node, until a shortest path tree is found. Several kinds of dual
updating operations are proposed, which allow one to derive different dual
algorithms from a general schema. One of them, in particular, which is based
only on global operations, can be viewed as a dual interpretation of
Dijkstra's classical algorithm.
Due to their structure, all the proposed approaches are suitable for
parallel implementations. They are also suitable for reoptimization approaches,
when the computation of shortest paths from different root nodes is required.
Università di Pisa
1996-03-01
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1935/1/TR-96-03.ps.gz
Pallottino, Stefano and Scutellà, Maria Grazia (1996) Dual Algorithms for the Shortest Path Tree Problem. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-03.ps.gz
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Design and evaluation of parallel applications using a structured parallel language
Pasetto, Davide
Vanneschi, Marco
INF/01 - Informatica
Structured parallel programming is one of the possible solutions to
exploit Programmability, Portability and Performance in the parallel
programming world.
Programming using high level parallel constructs permits the programmer to
focus on the development of the parallel algorithms rather than on their
low level implementation.
The power of this approach stands in the possibility of modeling the
performance of the high level constructs and building optimizing
template-based compilers.
These compilers use formulas describing the performance of language
constructs over the target architectures and tune their parametric
implementation to achieve high performance figures.
In this paper, we describe a set of applications developed using such a
programming methodology and show the results obtained.
Università di Pisa
1996-03-27
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1936/1/TR-96-06.ps.gz
Pasetto, Davide and Vanneschi, Marco (1996) Design and evaluation of parallel applications using a structured parallel language. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-06.ps.gz
oai:eprints.adm.unipi.it:1937
2014-12-09T10:06:00Z
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Combinatorial algorithms in the presence of random errors - II
Pedrotti, Alberto
INF/01 - Informatica
In the present study, we consider a computational model similar to the
classical RAM machine, except that each instruction performed by the
machine may fail with probability $q< 1/ 6e.$ The failures are
transient and independent of each other. The definition of this
model (which we call ERRAM) follows a previous work \cite{lp},
where we did not allow for addressing errors.
We show how an arbitrary RAM program may be transformed into an
ERRAM program, working with assigned probability $1- \delta,$ provided
that we know the number $T$ of instructions that are executed by the
original program, or an upper bound to it. One major tool that we use is
redundancy, namely, each operation is repeated a certain number of times,
and each stored value is kept in several copies. We derive upper
bounds on the amount of redundancy that is needed to achieve the desired
confidence. This allows us to bound both the space complexity and the
expected time complexity of the resulting ERRAM program, in terms of
$T$, $\delta$ and $q.$
Università di Pisa
1996-03-28
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1937/1/TR-96-07.ps.gz
Pedrotti, Alberto (1996) Combinatorial algorithms in the presence of random errors - II. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-07.ps.gz
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Machine independent Analytical models for cost evaluation of template--based programs
Pasetto, Davide
Vanneschi, Marco
INF/01 - Informatica
Structured parallel programming is one of the possible solutions to
exploit Programmability, Portability and Performance in the parallel
programming world.
The power of this approach stands in the possibility to build an optimizing
template--based compiler using low time complexity algorithms.
In order to optimize the code, this compiler needs formulas that describe
the performance of language constructs over the target architecture.
We propose a set of parameters able to describe current parallel systems
and build deterministic analytical models for basic forms of parallelism.
The analytical model describes construct performance in a parametric
way.This can be done by knowing that the compiler exploits a
template--based support and giving template implementors guidelines to
follow to make actual implementation perform as predicted.
Università di Pisa
1996-04-16
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1938/1/TR-96-08.ps.gz
Pasetto, Davide and Vanneschi, Marco (1996) Machine independent Analytical models for cost evaluation of template--based programs. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-08.ps.gz
oai:eprints.adm.unipi.it:1939
2015-01-26T07:50:03Z
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A hierarchy of constraint systems for data-flow analysis of constraint logic-based languages
Bagnara, Roberto
INF/01 - Informatica
Many interesting analyses for constraint logic-based languages
are aimed at the detection of \emph{monotonic} properties, namely
of properties which are preserved as the computation progresses.
Our basic claim is that most, if not all, of these analyses can be
described within a unified notion of constraint domains.
We present a class of constraint systems which allows
for a smooth integration within an appropriate framework for the
definition of non-standard semantics of constraint logic-based languages.
Such a framework is also presented and motivated.
We then show how such domains can be built, as well as construction
techniques which induce a hierarchy of domains.
In particular, we propose a general methodology for domain combination
with asynchronous interaction (i.e.~the interaction is not necessarily
synchronized with the domains' operations).
Following this methodology, interesting combinations of domains
can be expressed with all the the semantic elegance
of concurrent constraint programming languages.
Università di Pisa
1996-05-04
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1939/1/TR-96-10.ps.gz
Bagnara, Roberto (1996) A hierarchy of constraint systems for data-flow analysis of constraint logic-based languages. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-10.ps.gz
oai:eprints.adm.unipi.it:1940
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Assegnazione dei passeggeri a una rete pubblica interurbana mediante l'enumerazione dei cammini attivi
Pallottino, Stefano
Schettino, Alberta
INF/01 - Informatica
Viene descritta l'implementazione di un modello di assegnazione dei
passeggeri a una rete di trasporto interurbano con vincoli espliciti di
capacit\`a sui veicoli. Inizialmente vengono determinati i cammini attivi
rispetto a una soglia \epsilon, detta minimale, e successivamente viene
assegnata la domanda a detti cammini. Il codice di calcolo descritto
determina, oltre alla soglia minimale, anche il flusso di assegnazione.
Università di Pisa
1996-04-18
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1940/1/TR-96-09.ps.gz
Pallottino, Stefano and Schettino, Alberta (1996) Assegnazione dei passeggeri a una rete pubblica interurbana mediante l'enumerazione dei cammini attivi. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-09.ps.gz
oai:eprints.adm.unipi.it:1941
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Applying Refinement Calculi to Software Process Modelling
Montangero, Carlo
Semini, Laura
INF/01 - Informatica
A refinement calculus provides a number of advantages to
program development, besides correctness, like clarification
of the goals of the program and effective documentation of
the design choices. In this paper, we provide evidence that
the same advantages can be obtained also in the case of those
special programs that are known as enactable process models.
The evidence is put forward by means of an example, a small
Concurrent Engineering problem inspired to the IWSP7 problem.
We assume that the enactment is done by rules in tuple spaces,
and use a refinement calculus based on a temporal logic that
builds on that of Unity. Finally, we show how the approach
leads to seamless integration with existing process engines
(the Oikos one in our case).
Università di Pisa
1996-05-22
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1941/1/TR-96-18.ps.gz
Montangero, Carlo and Semini, Laura (1996) Applying Refinement Calculi to Software Process Modelling. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-18.ps.gz
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Confluence in Concurrent Constraint Programming
Falaschi, M.
Gabbrielli, M.
Marriott, K.
Palamidessi, C.
INF/01 - Informatica
Concurrent constraint programming (ccp), like most of the
concurrent paradigms, has a mechanism of global choice which makes
computations dependent on the scheduling of processes.
This is one of the main reasons
why the formal semantics of ccp is more complicated
than the one of its deterministic and local-choice sublanguages.
In this paper we study various subsets of ccp
obtained by adding some restriction on the notion of choice,
or by requiring confluency, i.e. independency from the scheduling
strategy.
We show that it is possible to define simple denotational semantics
for these subsets, for various notions of observables.
Finally, as an application of our results we develop a
framework for the compositional analysis of full ccp.
The basic idea is to approximate an arbitrary ccp program by
a program in the restricted language, and then analyze the latter,
by applying the standard techniques of abstract interpretation
to its denotational semantics.
Università di Pisa
1996-05-30
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1942/1/TR-96-21.ps.gz
Falaschi, M. and Gabbrielli, M. and Marriott, K. and Palamidessi, C. (1996) Confluence in Concurrent Constraint Programming. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-21.ps.gz
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A Reactive Implementation of \textit{Pos} Using ROBDDs
Bagnara, Roberto
INF/01 - Informatica
The subject of groundness analysis for (constraint) logic programs
has been widely studied, and interesting domains have been proposed.
\textit{Pos} has been recognized has the most suitable domain for
capturing the kind of dependencies arising in groundness analysis.
Its (by now standard) implementation is based on
\emph{reduced ordered binary-decision diagrams} (ROBDDs), a well-known
symbolic representation for Boolean functions. Even though several authors
have reported positive experiences using ROBDDs for groundness analysis,
in the literature there is no reference to the problem of the efficient
detection of those variable which are deemed to be ground in the context
of a ROBDD. This is not surprising, since most currently implemented
analyzers need to derive this information only \emph{at the end} of the
analysis and only for presentation purposes. Things are much different
when this information is required \emph{during} the analysis.
This need arises when dealing with languages which employ some sort
of \emph{delay mechanism}, which are typically based on groundness
conditions. In these cases, the \emph{na\"\i{}f} approaches are too
inefficient, since the abstract interpreter must quickly (and often)
decide whether a constraint is delayed or not. Fast access to ground
variables is also necessary when aliasing analysis is performed using
a domain not keeping track of ground dependencies.
In this paper we introduce and study the problem, proposing two possible
solutions. The second one, besides making
possible the quick detection of ground variables, has also the effect
of keeping the ROBDDs as small as possible, improving the efficiency
of groundness analysis in itself.
Università di Pisa
1996-05-24
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1943/1/TR-96-19.ps.gz
Bagnara, Roberto (1996) A Reactive Implementation of \textit{Pos} Using ROBDDs. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-19.ps.gz
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A Program Specialiser for Meta-level Compositions of Logic Programs
Brogi, Antonio
Contiero, Simone
INF/01 - Informatica
Meta-level compositions of object logic programs are naturally
implemented by means of meta-programming techniques.
Meta-interpreters defining program compositions however suffer
from a computational overhead that is due partly to the
interpretation layer present in all meta-programs, and
partly to the specific interpretation layer needed to
deal with program compositions.
We show that meta-interpreters implementing compositions
of object programs can be fruitfully specialised w.r.t.
meta-level queries of the form "Demo(E,G)" , where "E"
denotes a program expression and "G" denotes a (partially
instantiated) object level query.
More precisely, we describe the design and implementation
of a declarative program specialiser that suitably
transforms such
meta-interpreters so as to sensibly reduce --- if not
to completely remove --- the overhead due to the handling of
program compositions.
In many cases the specialiser succeeds in
eliminating also the overhead due to meta-interpretation.
Università di Pisa
1996-05-24
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1944/1/TR-96-20.ps.gz
Brogi, Antonio and Contiero, Simone (1996) A Program Specialiser for Meta-level Compositions of Logic Programs. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-20.ps.gz
oai:eprints.adm.unipi.it:1945
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Verification of Meta-interpreters
Pedreschi, Dino
Ruggieri, Salvatore
INF/01 - Informatica
A novel approach to the verification of meta-interpreters is
introduced. We apply
a general purpose verification method for logic programs,
proposed by the authors,
to the case study of the Vanilla and other logic meta-interpreters.
We extend the standard notion of declarative correctness,
and design a criterion for proving
correctness of meta-interpreters in a general sense, including
amalgamated and reflective meta-interpreters.
The contribution of this paper can be summarized as follows:
under certain
natural assumptions, all interesting verification
properties lift up from the
object program to the meta-program, including
partial correctness, termination,
absence of errors, call patterns persistence,
correct instances of queries,
computed instances of queries.
Interestingly, it is possible to
establish these results on the basis of purely
declarative reasoning, using the mentioned proof method.
We believe that the obtained results illustrate
the broad applicability of the adopted verification principles.
Università di Pisa
1996-06-07
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1945/1/TR-96-23.ps.gz
Pedreschi, Dino and Ruggieri, Salvatore (1996) Verification of Meta-interpreters. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-23.ps.gz
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Modular Verification of Logic Programs
Pedreschi, Dino
Ruggieri, Salvatore
INF/01 - Informatica
Recentely, a new approach to verification of
logic and Prolog programs has been proposed, whose main advantage is
the possibility to reason on different properties in a unified
framework. In this paper, we show an equivalent formulation of that
proof method which is well-suited for modular program
verification. The notion of modularity taken into account is based on
stratification.
We show that the proofs of correctness of a program P
and a program Q can be re-used in the proof of correctness of
P "union" Q with small additional efforts. The main advantage consists in
the fact that the proofs for P and Q are developed in a fully
independent way.
Università di Pisa
1996-06-18
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1946/1/TR-96-24.ps.gz
Pedreschi, Dino and Ruggieri, Salvatore (1996) Modular Verification of Logic Programs. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-24.ps.gz
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Hyperflow Models
Gallo, Giorgio
Scutellà, Maria Grazia
INF/01 - Informatica
We consider the Minimum cost hyperflow problem, a generalization of the
minimum cost flow problems on standard and on generalized graphs. In order
to solve this problem, a specialization of the primal Simplex Algorithm,
named the Hypergraph Simplex Algorithm, has been recently proposed. Here,
the results of a wide experimentation on random hypergraphs and on some
kinds of
structured hypergraphs are reported. In the experimentation, a C implementation
of the Hypergraph Simplex Algorithm has been compare wth the primal version
of CPLEX code, by obtaining rather interesting results. In fact, when the
hypergraph size increases, our code runs faste than CPLEX; in particular,
its solution time is a rather slow increasing fnction of the hypergraph size.
The problem under consideration has very interesting applications, which
can be modelled and solved in terms of hypergraph flows. These include
Multicommodity flows and applications in the area of flexible manufacturing
systems, like the One-Dimensional Cutting Stock Problem and Assembly Problems.
In particular, it is shown how to model Assembly Problems with a given degree,
say k, of parallelism (i.e. when k parallel identical machinesare available
for the execution of the operations) in terms of hyperflows. Finally, some
Economic Applications are formulated and interpreted in terms of minimum cost
hyperflow problems.
Università di Pisa
1996-07-01
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1947/1/TR-96-26.ps.gz
Gallo, Giorgio and Scutellà, Maria Grazia (1996) Hyperflow Models. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-26.ps.gz
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Compact Transition Systems
Degano, Pierpaolo
Priami, Corrado
INF/01 - Informatica
A major drawback of representing concurrent systems as transition systems
is the exponential size of their semantic representations. We present a way of
obtaining compact transition systems that are mildly exponential in
average. The idea is to have (at least) one computation
to represent all the ones only differing for the
temporal ordering in which concurrent transitions occur.
We characterise through axioms the
transition systems which may be reduced in size, still preserving
non interleaving bisimulation equivalences.
We also exemplify our reduction technique on a process calculus
whose compact transition system is generated in SOS style.
Università di Pisa
1996-07-09
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1948/1/TR-96-28.ps.gz
Degano, Pierpaolo and Priami, Corrado (1996) Compact Transition Systems. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-28.ps.gz
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The Tile Model
Gadducci, Fabio
Montanari, Ugo
INF/01 - Informatica
In this paper we introduce a model for a wide class of computational
systems, whose behaviour can be described by certain rewriting rules.
We gathered our inspiration both from the world of term rewriting, in
particular from the {\em rewriting logic} framework \cite{Mes92}, and of
concurrency theory: among the others, the
{\em structured operational semantics} \cite{Plo81}, the {\em context systems}
\cite{LX90} and the {\em structured transition systems} \cite {CM92}
approaches.
Our model recollects many properties of these sources: first, it provides
a compositional way to describe both the states and the sequences of
transitions performed by a given system, stressing their distributed nature.
Second, a suitable notion of typed proof allows to take into account also
those formalisms relying on the notions of {\em synchronization} and
{\em side-effects} to determine the actual behaviour of a system.
Finally, an equivalence relation over sequences of transitions is defined,
equipping the system under analysis with a concurrent
semantics, where each equivalence class denotes a family of
``computationally equivalent'' behaviours, intended to correspond to the
execution of the same set of (causally unrelated) events.
As a further abstraction step, our model is conveniently represented using
double-categories: its operational semantics is recovered with a free
construction, by means of a suitable adjunction.
Università di Pisa
1996-06-30
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1949/1/TR-96-27.ps.gz
Gadducci, Fabio and Montanari, Ugo (1996) The Tile Model. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-27.ps.gz
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Algebraic Approaches to Graph Transformation, Part I: Basic Concepts and Double Pushout Approach
Corradini, Andrea
Montanari, Ugo
Rossi, Francesca
Ehrig, H.
Heckel, Reiko
Loewe, M.
INF/01 - Informatica
The algebraic approaches to graph transformation are based on the
concept of gluing of graphs, modelled by pushouts in suitable
categories of graphs and graph morphisms. This allows one not only to give
an explicit algebraic or set theoretical description of the
constructions, but also to use concepts and results from category
theory in order to build up a rich theory and to give elegant proofs
even in complex situations.
In this chapter we start with an overwiev of the basic notions common
to the two algebraic approaches, the "double-pushout (DPO) approach" and
the "single-pushout (SPO) approach"; next we present the classical
theory and some recent development of the double-pushout approach. The next
chapter is devoted instead to the single-pushout approach, and it is closed
by a comparison between the two approaches.
--
This document will appear as a chapter of the "The Handbook of Graph Grammars.
Volume I: Foundations" , G. Rozenberg (Ed.), World Scientific.
Università di Pisa
1996-03-21
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1950/1/TR-96-17.ps.gz
Corradini, Andrea and Montanari, Ugo and Rossi, Francesca and Ehrig, H. and Heckel, Reiko and Loewe, M. (1996) Algebraic Approaches to Graph Transformation, Part I: Basic Concepts and Double Pushout Approach. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-17.ps.gz
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DEMOS at CONCUR96
Priami, Corrado
INF/01 - Informatica
Those that follow are the abstracts of the demonstrations at the CONCUR
conference held in Pisa in August 1996. The demonstrations cover
different aspects of theory of concurrency. They range from process
algebras verifiers to model checkers as well as Petri nets support tools.
There are also demonstrations on the check of security properties and
performance analysis based on process algebra descriptions. Finally, a
demonstration of game aspects with CWB is presented.
Università di Pisa
1996-08-22
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1951/1/TR-96-29.ps.gz
Priami, Corrado (1996) DEMOS at CONCUR96. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-29.ps.gz
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A Rewriting Implementation of pi-calculus
Viry, Patrick
INF/01 - Informatica
We introduce a rewriting implementation of the reduction relation of
$\pi$-calculus and prove its correctness. The implementation is based
on terms with De Bruijn indices and an explicit substitution
operator. The resulting rewrite rules need to be applied modulo a
large and complex equational theory, and are only of theoretical
interest. Applying the coherence techniques introduced in a previous
paper, we transform this specification into an equivalent one that only
requires rewriting modulo associativity and commutativity. This latter
rewrite system can then be straightforwardly encoded in currently
available rewriting-based programming languages. Finally, we sketch a
possible application of this implementation as the basis for
adding input-output capabilities to such languages.
Università di Pisa
1996-03-26
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1952/1/TR-96-30.ps.gz
Viry, Patrick (1996) A Rewriting Implementation of pi-calculus. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-30.ps.gz
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Venticinque anni di informatica
Degano, Pierpaolo
INF/01 - Informatica
Atti della giornata per il venticinquennale del Corso di Laurea in
Scienze dell'Informazione
Proceedings of the silver jubilee of the Computer Science curriculum
Università di Pisa
1996-09-16
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1953/1/TR-96-32.ps.gz
Degano, Pierpaolo (1996) Venticinque anni di informatica. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-32.ps.gz
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An Insight on PRAM Computational Bounds
Luccio, Fabrizio
Pagli, Linda
INF/01 - Informatica
We make two contributions to the theory of PRAM computation, focusing on
the problem of computing the Boolean OR (to which most
basic problems can be reconducted).
First we critically discuss the ideal PRAM model generally adopted to
prove parallel time bounds, and introduce the natural definition
of simple PRAM. We prove that log(base 2) n
steps are needed to compute the OR of n bits in the CREW variant of
this model, and that this bound is tight.
This implies that some acclaimed "surprising" results in PRAM theory
depend strictly on the properties of the model, and not on the
computed function. As a second contribution we show how to simplify
the most advanced known lower bound proof for computing the OR.
The new proof scheme does not introduce new results,
but is aimed to enhancing the comprehension of this difficult subject.
We also justify a "full information" functioning,
generally adopted without discussion.
Università di Pisa
1996-06-28
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1954/1/TR-96-25.ps.gz
Luccio, Fabrizio and Pagli, Linda (1996) An Insight on PRAM Computational Bounds. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-25.ps.gz
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The Nice Properties of a New Boolean Function
Luccio, Fabrizio
Pagli, Linda
INF/01 - Informatica
\begin{abstract}
We work in $B^n$
and consider sets of $2^m$ points, $m \leq n$, represented in
binary {\em balanced}
matrices, whose columns contain half 0's and half 1's, and this
property repeats recursively in proper submatrices. We introduce
the concept of {\em pseudo-cube} of order $m$,
that is a subset of $2^m$ points of $B^n$ whose matrix is balanced. A
subcube $B^m \subseteq B^n$ is a special case of pseudo-cube and shares
most of its properties. For a given pseudo-cube $P$ we define
the class ${\cal P}(P)$ of the pseudo-cubes obtained from $P$ by
complementing any subset of variables, and show that the elements of
${\cal P}(P)$ are disjoint and tessellate $B^n$. Furthermore,
the union of any two
pseudo-cube of the same class ${\cal P}$ is a pseudo-cube,
and the intersection of two arbitrary pseudo-cubes is either
empty or is a pseudo-cube.
We then introduce {\em pseudo-products} as Boolean
functions that
have value 1 in the points of a pseudo-cube $P$. These functions
inherit all the properties of pseudo-cubes, and have a compact expression
EXP($P$).
Given two pseudo-products $P_1$, $P_2$ belonging to the same class
$\cal P$, we give an algorithm to construct in linear time
the expression of the union EXP($P_1 \cup P_2$)
from EXP($P_1$) and EXP($P_2$).
Finally we show how a standard procedure to generate a
minimal "sum of products" form for a Boolean function $f$ can be extended
to generate a minimal "sum of pseudo-products" for $f$. This latter form,
based
on the representation EXP, is generally much shorter than the
corresponding Boolean form.
\end{abstract}
Università di Pisa
1996-10-15
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1955/1/TR-96-33.ps.gz
Luccio, Fabrizio and Pagli, Linda (1996) The Nice Properties of a New Boolean Function. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-33.ps.gz
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Parsing MELL Proof Nets
Guerrini, S.
Masini, A.
INF/01 - Informatica
We propose a new formulation for full (weakening and constants
included) multiplicative and exponential (MELL) proof nets,
allowing a complete set of rewriting rules to parse them. The
recognizing grammar defined by such a rewriting system (confluent
and strong normalizing on the new proof nets) gives a correctness
criterion that we show equivalent to the Danos-Regnier one.
Università di Pisa
1996-10-25
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1956/1/TR-96-34.ps.gz
Guerrini, S. and Masini, A. (1996) Parsing MELL Proof Nets. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-34.ps.gz
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Sistema di protezione per il Dipartimento di Informatica
Ambriola, Vincenzo
Telmon, Claudio
INF/01 - Informatica
In questo lavoro si descrive il progetto del sistema di
protezione per il sistema informatico del Dipartimento di
Informatica. Nella progettazione si è tenuto conto delle
peculiarità di questo tipo di organizzazioni di ricerca. Si tratta
di organizzazioni tradizionalmente aperte, il cui principale
interesse consiste nella disponibilità delle risorse piu` che
nella riservatezza dei dati trattati. Il progetto ha quindi come
principale obiettivo la protezione di alcune risorse essenziali
dalle quali è possibile ripristinare uno stato corretto sui
principali sistemi del Dipartimento. Fa eccezione la sottorete
amministrativa, per la quale devono essere garantite anche la
riservatezza e l'integrità dei dati. Il progetto, completato
nell'aprile 1996, è in fase avanzata di realizzazione.
Università di Pisa
1996-10-25
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1957/1/TR-96-35.ps.gz
Ambriola, Vincenzo and Telmon, Claudio (1996) Sistema di protezione per il Dipartimento di Informatica. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-35.ps.gz
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Symmetric and Asymmetric Parallelization of a Cost-Decomposition Algorithm for Multi-Commodity Flow Problems
Cappanera, Paola
Frangioni, Antonio
INF/01 - Informatica
Abstract: We study the coarse-grained parallelization of a Bundle-based
cost decomposition algorithm for the solution of linear Multicommodity Min
Cost Flow problems, that has already been shown to be effective in
sequential. The aim of the study was to investigate if exploitation of the
natural parallelism inherent in the cost decomposition method, i.e. the
simultaneous solution of the Min Cost Flow subproblems, was enough to
obtain acceptable efficiencies without modifying the basic approach: as a
result, we obtained an highly portable and flexible code which can be used
on different machines. The computational results show that satisfactory
efficiencies can be obtained even with many processors on large, difficult
MMCF problems with many commodities, that are exactly the class of
instances where the sequential code attains the best results. We also show
how to exploit a common characteristic of nowadays supercomputer
facilities, i.e. the side-to-side availability of massively parallel and
powerful vector supercomputers, by implementing an asymmetric decomposition
algorithm where each architecture is used for the tasks it is suited most.
Università di Pisa
1996-11-07
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1958/1/TR-96-36.ps.gz
Cappanera, Paola and Frangioni, Antonio (1996) Symmetric and Asymmetric Parallelization of a Cost-Decomposition Algorithm for Multi-Commodity Flow Problems. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-36.ps.gz
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Il monitoraggio del processo software: una soluzione dal punto di vista del committente
Ambriola, Vincenzo
Cignoni, Giovanni A.
INF/01 - Informatica
According to the Italian law, monitoring is a form of quality
control that must be performed in the enactment of all the contracts
of great importance related to the information systems of the Italian
Public Administration. In this paper, the authors describe and
analyse the aspects of monitoring as a tool to guarantee the quality
of software production and, as a consequence, to assure the customer
satisfaction. The paper presents the administrative context where
monitoring is applied, its purpose and the application areas, the
relationship with other forms of quality control. In particular, we
emphasise the novelty of monitoring and its characteristic of customer
initiative.
Università di Pisa
1996-10-31
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1959/1/TR-96-37.ps.gz
Ambriola, Vincenzo and Cignoni, Giovanni A. (1996) Il monitoraggio del processo software: una soluzione dal punto di vista del committente. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-37.ps.gz
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Testing Optimality for Quadratic 0-1 Problems
Carraresi, Paolo
Farinaccio, Fernanda
Malucelli, Federico
INF/01 - Informatica
Abstract: The issue tackled is testing whether a given solution of a quadratic 0-1 problem is optimal. The paper presents an algorithm based on the necessary and sufficient optimality condition introduced by Hirriart-Urruty for general convex problems. A measure of the quality of the solution is provided. Computational results show the applicability of the method. The method is extended to constrained quadratic 0-1 problems such as quadratic assignment and quadratic knapsack .
Università di Pisa
1996-12-03
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1960/1/TR-95-11.ps.gz
Carraresi, Paolo and Farinaccio, Fernanda and Malucelli, Federico (1996) Testing Optimality for Quadratic 0-1 Problems. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-95-11.ps.gz
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A Fast Iterative Method for Determining the Stability of a Polynomial
Gemignani, Luca
INF/01 - Informatica
We present an iterative numerical method for
solving two classical stability problems for
a polynomial $p(x)$ of degree $n$: the
Routh-Hurwitz and the Schur-Cohn
problems. This new method relies on
the construction of a polynomial sequence
$\{ p^{(k)}(x) \}_ {k\in {\bf
N}}$, $p^{(0)}(x)=p(x)$ , such that $p^{(k)}(x)$
quadratically converges to $(x-1)^p
(x+1)^{n-p}$ whenever the starting polynomial
$p(x)$ has
$p$ zeros with positive real parts and $n-p$
zeros with negative real parts.
By combining some
new results
on structured matrices with the fast polynomial arithmetic, we prove that the
coefficients of $p^{(k)}(x)$ can be computed
starting from the coefficients of
$p^{(k-1)}(x)$ at the computational cost of
$O(n\log^2 n)$ arithmetical operations.
Moreover, by means of numerical experiments, we show that the $O(n\log n)$ bit precision of
computations suffices to support the stated computational properties.
In this way, apart from
a logarithmic factor, we arrive at the current best upper bound of $O(n^3\log^4 n)$ for the
bit complexity of the mentioned stability problems.
Università di Pisa
1996-05-16
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1961/1/TR-96-12.ps.gz
Gemignani, Luca (1996) A Fast Iterative Method for Determining the Stability of a Polynomial. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-12.ps.gz
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Fast QR Factorization of Vandermonde-like matrices involving orthogonal polynomials
Gemignani, Luca
INF/01 - Informatica
Fast orthogonalization schemes for m\times n Vandermonde matrices
V=(z_i^j), introduced by Demeure, are extended to compute both a
$QR$ factorization and an inverse QR factorization of
Vandermonde-like
matrices P=(p_j(z_i)) where the polynomials
p_j(z) satisfy a three-term
recurrence relation. In this way we are able
to solve least squares (LS)
problems
of the form
\begin{eqnarray*}
{\rm minimize } \ ||{\bf b}-P{\bf x}||_2
\end{eqnarray*}
using only O(mn) arithmetical operations and O(m) storage.
\end{abstract}
\bigskip
Università di Pisa
1996-05-16
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1962/1/TR-96-11.ps.gz
Gemignani, Luca (1996) Fast QR Factorization of Vandermonde-like matrices involving orthogonal polynomials. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-11.ps.gz
oai:eprints.adm.unipi.it:1963
2015-01-26T13:30:20Z
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A Fast Algorithm for Hankel Matrices Represented in Orthogonal Polynomial Bases
Gemignani, Luca
INF/01 - Informatica
Consider a $n \times n$ lower triangular matrix $L$ whose
$(i+1)$-st row is defined by the coefficients of the real
polynomial $p_i(x)$ of degree $i$ such that
$\{ p_i(x)\}$ is a set of orthogonal polynomials
satisfying a standard three-term
recurrence relation.
If $H$ is a $n\times n$ real Hankel matrix with nonsingular
leading principal submatrices, then $\widehat{H}=L HL^T$ will be referred
as a strongly nonsingular Hankel matrix with respect to the
orthogonal polynomial basis $\{p_i(x)\}$.
In this paper we develop an efficient
$O(n^2)$ algorithm for the solution of a system of linear equations with a
real symmetric coefficient matrix $\widehat{H}$ which is a Hankel matrix
with respect to a suitable orthogonal polynomial basis. We then apply our
method to the solution of a weighted
finite moment problem.
Università di Pisa
1996-05-16
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1963/1/TR-96-13.ps.gz
Gemignani, Luca (1996) A Fast Algorithm for Hankel Matrices Represented in Orthogonal Polynomial Bases. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-13.ps.gz
oai:eprints.adm.unipi.it:1964
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POLYNOMIAL ROOT COMPUTATION BY MEANS OF THE LR ALGORITHM
Gemignani, Luca
INF/01 - Informatica
By representing the $LR$ algorithm of Rutishauser and its variants in a
polynomial setting, we derive
numerical methods for approximating either all of the roots
or a number $k$ of the roots of minimum modulus
of a given polynomial $p(t)$ of degree $n$. These methods share the
convergence properties of the $LR$ matrix iteration but, unlike it,
they
can be arranged to produce parallel and sequential
algorithms which are highly efficient
expecially in the case where $k<<n$.
Università di Pisa
1996-05-16
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1964/1/TR-96-16.ps.gz
Gemignani, Luca (1996) POLYNOMIAL ROOT COMPUTATION BY MEANS OF THE LR ALGORITHM. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-16.ps.gz
oai:eprints.adm.unipi.it:1965
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From string rewriting to logical metabolic systems
Manca, Vincenzo
Martino, D. M.
INF/01 - Informatica
In this paper we focus on the notion of metabolism and the way it can be
expressed in symbolic terms. We show as an adequate logical
formalization of this concept could help to unify several approaches based
in string rewriting mechanism. This viewpoint suggests new perspectives
in the search for more powerful and general methods in the description
of symbolic dynamical systems where evolution obeys some internal laws
of structural recombination (L-systems, Grammar systems, H-systems,
Ecogrammars, DNA computing models).
Università di Pisa
1997-01-13
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1965/1/TR-97-01.ps.gz
Manca, Vincenzo and Martino, D. M. (1997) From string rewriting to logical metabolic systems. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-01.ps.gz
oai:eprints.adm.unipi.it:1966
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Programming by Combining General Logic Programs
Brogi, Antonio
Contiero, Simone
Turini, Franco
INF/01 - Informatica
The program composition approach can be fruitfully applied to combine
general logic programs, i.e. logic programs possibly containing
negative premises.
We show how the introduction of a basic set of (meta-level) composition
operations over general programs increases the knowledge representation
capabilities of logic programming for non-monotonic reasoning.
Examples of modular programming, hierarchical reasoning, constraints
and rules with exceptions will be illustrated.
The semantics of programs and program compositions is defined in terms
of three-valued logic. The computational interpretation of program
compositions is formalised by an equivalence preserving syntactic
transformation of arbitrary program compositions into standard general
programs.
Università di Pisa
1997-01-13
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1966/1/TR-97-02.ps.gz
Brogi, Antonio and Contiero, Simone and Turini, Franco (1997) Programming by Combining General Logic Programs. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-02.ps.gz
oai:eprints.adm.unipi.it:1967
2015-01-23T10:11:11Z
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GCD of polynomials and Bezout matrices
Gemignani, Luca
INF/01 - Informatica
A new algorithm is presented for computing
an integer polynomial similar to the GCD of
two polynomials $u(x)$ and $v(x)$ $\in {\bf Z}[x]$, $\deg(u(x))=n\geq
\deg(v(x)) $. Our approach uses structured matrix
computations involving Bezout matrices rather than
Hankel matrices. In this way we reduce the computational costs
showing that the new algorithm requires $O(n^2)$ arithmetical
operations or $O(n^4(\log^2 n +l^2))$ Boolean operations,
where $l=\max
\{ \log(\parallel u(x) \parallel_{\infty}), \log(\parallel v(x)
\parallel_{\infty})\}$.
Università di Pisa
1997-01-13
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1967/1/TR-97-03.ps.gz
Gemignani, Luca (1997) GCD of polynomials and Bezout matrices. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-03.ps.gz
oai:eprints.adm.unipi.it:1968
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MANIPULATING POLYNOMIALS IN GENERALIZED FORM
Gemignani, Luca
INF/01 - Informatica
We present new algorithms using structured
matrix methods for manipulating polynomials
expressed in generalized form,
that is, relative to a polynomial basis $\{p_i(x)\}$ satisfying
a three-term recurrence relation. This includes computing
the Euclidean remainders as well as the greatest common divisor
of two polynomials $u(x)$ and $v(x)$ of degrees less than $n$.
The computational schemes
involve solving linear systems with nested Hankel matrices
represented
in the given generalized basis and they reach the optimal
sequential complexity of $O(n^2)$ arithmetical operations.
Università di Pisa
1996-12-23
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1968/1/TR-96-14.ps.gz
Gemignani, Luca (1996) MANIPULATING POLYNOMIALS IN GENERALIZED FORM. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-14.ps.gz
oai:eprints.adm.unipi.it:1969
2015-01-23T10:10:57Z
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http://eprints.adm.unipi.it/1969/
RATIONAL INTERPOLATION AT CHEBYSHEV POINTS
Gemignani, Luca
INF/01 - Informatica
The Lanczos method and its variants can be used to solve
efficiently the
rational interpolation problem.
In this paper we present
a suitable fast modification
of a general look-ahed version of
the Lanczos process
in order to deal with polynomials
expressed in the Chebyshev
orthogonal
basis. The proposed approach is particularly
suited for rational interpolation at Chebyshev points,
that is, at the zeros of Chebyshev polynomials.
In fact, in this case it overcomes
some of the numerical difficulties which limited the applicability
of the look-ahed Lanczos process for determining the coefficients both of
the numerators and of the denominators with respect to the standard power basis.
Università di Pisa
1996-12-23
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1969/1/TR-96-15.ps.gz
Gemignani, Luca (1996) RATIONAL INTERPOLATION AT CHEBYSHEV POINTS. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-96-15.ps.gz
oai:eprints.adm.unipi.it:1970
2015-01-23T10:11:38Z
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Using MPI for P3L Implementation
Manconi, Carlo
Cantalupo, Barbara
INF/01 - Informatica
This document concerns with the implementation of the P3L parallel
programming language on the MPI abstract Machine. First we focus our
attention on the characteristics of the MPI Abstract Machine, then we
present a preliminary implementaton for each P3L construct based on
that architecture.
Università di Pisa
1997-02-06
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1970/1/TR-97-04.ps.gz
Manconi, Carlo and Cantalupo, Barbara (1997) Using MPI for P3L Implementation. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-04.ps.gz
oai:eprints.adm.unipi.it:1971
2015-01-23T10:11:29Z
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http://eprints.adm.unipi.it/1971/
Verification of Logic Programs
Pedreschi, Dino
Ruggieri, Salvatore
INF/01 - Informatica
We propose a proof method in the style of Hoare's logic,
aimed at providing a unifying framework for the verification of
logic and Prolog programs with respect to their specifications.
The method, which relies on purely declarative
reasoning, has been designed as a trade-off
between expressive power and ease of use.
On the basis of a few simple principles, we
reason uniformly on several properties of logic and
Prolog programs, including partial correctness, total
correctness, absence of run-time errors, safe omission of the
occur-check, computed answers, modular program
development.
We finally generalize the method to general programs.
Università di Pisa
1997-02-10
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1971/1/TR-97-05.ps.gz
Pedreschi, Dino and Ruggieri, Salvatore (1997) Verification of Logic Programs. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-05.ps.gz
oai:eprints.adm.unipi.it:1972
2015-01-23T10:12:07Z
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http://eprints.adm.unipi.it/1972/
Shortest Path Algorithms in Transportation models: classical and innovative aspects
Pallottino, Stefano
Scutellà, Maria Grazia
INF/01 - Informatica
Shortest Path Problems are among the most studied network flow optimization
problems, with
interesting applications in various fields. One of such field is
transportation,
where shortest path problems of different kinds need to be solved.
Due to the nature of the application, transportation scientists need very
flexible and efficient shortest path procedures, both from the running time
point of view, and also for the memory requirements. Since no "best"
algorithm currently exists for every kind of transportation problem, research
in this field has recently moved to the design and implementation of "ad hoc"
shortest path procedures, which are able to capture the peculiarities of
the problems under consideration.
The aim of this work is to present in a unifying framework both the main
algorithmic approaches that have been proposed in the past years for solving
the shortest path problems arising most frequently in the transportation
field, and also some important implementaion techniques which allow one to
derive efficient procedures from the general algorithmic schema, in line
with trends in current research.
In the first part of the paper, afetr presenting the problem, we review those classical
primal and dual algorithms which seem to be the most interesting in transportation.
Promising reoptimization approaches are then discussed. The second part is devoted
to dynamic shortest path problems, which arise very frequently in the transportation
field. We analyse the main features and propose a general "chronological"
algorithmic paradigm, called Chrono-SPT. We study several special cases, and
investigate promising research avenues related to various extensions (time-windows.
turn penalties, multicriteria and shortest hyperpaths).
Università di Pisa
1997-04-14
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1972/1/TR-97-06.ps.gz
Pallottino, Stefano and Scutellà, Maria Grazia (1997) Shortest Path Algorithms in Transportation models: classical and innovative aspects. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-06.ps.gz
oai:eprints.adm.unipi.it:1973
2015-01-23T10:11:57Z
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http://eprints.adm.unipi.it/1973/
A survey on DNA computing
Pisanti, Nadia
INF/01 - Informatica
The aim of this report is to make a review on DNA computing: molecular
biology is used to suggest a new way of solving a NP-complete problem. The
idea (due to Leonard Adleman in [Adl94]) is to use strands of DNA to encode
the (instance of the) problem, and to manipulate them using techniques
commonly available in any molecular biology laboratory, in order to simulate
operations that select the solution of the problem, if it exists. After
Adleman's paper (appeared on "Science" in November 1994), many authors have
been interested in DNA computing. We will try to give a description of the
discussions and the results which appeared in literature.
Università di Pisa
1997-04-16
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1973/1/TR-97-07.ps.gz
Pisanti, Nadia (1997) A survey on DNA computing. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-07.ps.gz
oai:eprints.adm.unipi.it:1974
2015-01-23T10:11:50Z
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http://eprints.adm.unipi.it/1974/
A hybrid approach to some stability problems for bivariate polynomials
Gemignani, Luca
INF/01 - Informatica
Frequently, in control system design, we are asked to locate the roots of a bivariate
polynomial
of the following form
\begin{eqnarray*}
H(s,k)=\sum_{i=0}^n Q_i(s) k^i\in {\bf Z}[k,s]={\bf Z}[k][s]={\bf D}[s],
\end{eqnarray*}
where $Q_i(s)\in {\bf Z}[s]$ for each $i$ and, moreover,
$k$ is a free parameter
ranging in some real interval.
For a fixed value $\bar k$ of $k$, the zero distribution
of the univariate polynomial $p(s)=H(s,\bar k)$
with respect
to the imaginary axis
can be found by determining the inertia of a
Bezout matrix $B=B(\bar k)$
whose entries
are expressed in terms of the coefficients of $p(s)$.
This evaluation is usually
accomplished by
computing a block factorization of $B$, namely,
$U^TBU=D$ where $D$ is a block diagonal matrix
with lower triangular blocks with respect to the antidiagonal.
It is intended in this paper to propose an efficient
hybrid approach for determining the zero-distribution of $H(s,k)$
with respect to the
imaginary axis for any value of $k$.
We develop a fast
fraction-free
method for factoring the Bezout matrix $B(k)$ with
entries over ${\bf D}$ determined by
$H(s,k)\in {\bf D}[s]$. In this way,
we easily compute the sequence
$\{\phi_i(k)\}$ of the trailing principal minors
of $B(k)$. For almost any value $\bar k$ of
$k$ the associated
sign sequence $\{sign(\phi_i(\bar k))\}$ specifies
the inertia of $B(\bar k)$
and, therefore, the zero-distribution of $H(s,\bar k)$.
The function
$sign(\phi_i( k))$ is finally obtained
by numerically computing rational approximations of the
real zeros of $\phi_i(k)\in {\bf Z}[k]$.
Università di Pisa
1997-05-02
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1974/1/TR-97-08.ps.gz
Gemignani, Luca (1997) A hybrid approach to some stability problems for bivariate polynomials. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-08.ps.gz
oai:eprints.adm.unipi.it:1975
2015-01-23T10:11:43Z
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Logical Formalizations of Syntactical Properties (Extended Abstract)
Manca, Vincenzo
INF/01 - Informatica
In this paper first order logic is used for expressing syntax of formal
languages. A model Syn is introduced and it is shown that whitin it
syntactic relations and classes of languages are representable by means of
first order formulae. The class of Sigma*(1) formulae is defined as an
extension of arithmetical Sigma(1) formulae; then, a theory is considered
where many syntactical notions can be developed in terms of axiomatic
representability.
This logical approach seems adequate to analyze and to integrate in a unique
framework several grammatical models that emerge in the search for new
computational paradigms.
Università di Pisa
1997-06-23
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1975/1/TR-97-10.ps.gz
Manca, Vincenzo (1997) Logical Formalizations of Syntactical Properties (Extended Abstract). Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-10.ps.gz
oai:eprints.adm.unipi.it:1976
2015-01-23T10:12:27Z
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Abductive analysis of modular logic programs
Giacobazzi, Roberto
INF/01 - Informatica
We introduce a practical method for abductive analysis of
modular logic programs. This is obtained by reversing the deduction process,
which is usually applied in static-dataflow analysis of logic programs,
on generic, possibly abstract, domains for analysis.
The approach is validated in the framework of abstract interpretation.
The abduced information provides an abstract specification for program
modules which can be of assistance both in top-down development
of programs and in compile-time optimization.
To the best of our knowledge this is the first application of abductive
reasoning in dataflow analysis of logic programs.
Università di Pisa
1997-06-25
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1976/1/TR-97-11.ps.gz
Giacobazzi, Roberto (1997) Abductive analysis of modular logic programs. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-11.ps.gz
oai:eprints.adm.unipi.it:1977
2015-01-23T10:12:19Z
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Lifting complete orders to achieve co-additivity of closure operators
Giacobazzi, Roberto
Ranzato, Francesco
INF/01 - Informatica
We define the notion of meet-uniformity for closure operators on a
complete lattice, which corresponds to co-additivity restricted to subsets
mapped into the same element, and we study its properties. A class of
closures given by principal filters and the downward closures
are relevant examples of meet-uniform closures. Next, we introduce a
lifting of a complete order by means of a meet-uniform closure.
Our main results show that this lifting preserves the complete
lattice structure, and allows the meet-uniform closure to become
fully co-additive.
Università di Pisa
1997-06-25
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1977/1/TR-97-12.ps.gz
Giacobazzi, Roberto and Ranzato, Francesco (1997) Lifting complete orders to achieve co-additivity of closure operators. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-12.ps.gz
oai:eprints.adm.unipi.it:1978
2015-01-23T10:12:13Z
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Functional Compositions of Abstract Interpretations
Giacobazzi, Roberto
Ranzato, Francesco
INF/01 - Informatica
In the context of standard abstract interpretation theory, we define
and study a systematic operator of reduced relative power for
composing functionally abstract domains. The reduced relative power of
two abstract domains D1 (the exponent) and D2 (the base)
consists in a suitably defined lattice of monotone functions from
D1 to D2, called dependencies, and it is a generalization of the
Cousot and Cousot operator of reduced (cardinal) power. The
relationship between the reduced relative power and Nielson's tensor
product is also investigated. The case of autodependencies (when base
and exponent are the same domain) turns out to be particularly
interesting: Under certain hypotheses, the domain of autodependencies
corresponds to a suitable powerset-like completion of the base
abstract domain, providing a compact lattice-theoretic representation
for autodependencies. The usefulness of the reduced relative power is
shown by a number of applications to abstract domains used both for
program analysis and for semantics design. Notably, we prove that the
domain Def for logic program ground-dependency analysis can be
characterized as autodependencies of a standard more abstract domain
representing plain groundness only, and we show how to exploit reduced
relative power to systematically derive compositional logic program
semantics.
Università di Pisa
1997-07-02
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1978/1/TR-97-13.ps.gz
Giacobazzi, Roberto and Ranzato, Francesco (1997) Functional Compositions of Abstract Interpretations. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-13.ps.gz
oai:eprints.adm.unipi.it:1979
2015-01-23T10:13:47Z
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http://eprints.adm.unipi.it/1979/
(Cyclic) Term Graph Rewriting is adequate for Rational Parallel Term Rewriting
Corradini, Andrea
Drewes, Frank
INF/01 - Informatica
"Acyclic" Term Graphs are able to represent terms with sharing,
and the relationship between Term Graph Rewriting (TGR)
and Term Rewrtiting (TR) is
now well understood. During the last years, some
researchers considered the extension of TGR to possibly "cyclic"
term graphs, which can
represent possibly infinite, rational terms. In [Kennaway et.al.,1994]
the authors formalize the classical relationship between TGR and TR as an
"adequate mapping" between rewriting systems, and extend it by
proving that unraveling is an adequate mapping from cyclic TGR to
rational, infinitary term rewriting: In fact, a single graph
reduction may correspond to an infinite sequence of term reductions.
Using the same notions, we propose a different adequacy result,
showing that unraveling is an adequate mapping from cyclic TGR to
"rational parallel term rewriting" , where at each
reduction infinitely many rules can be applied in parallel.
We also argue that our adequacy result is more
natural than that proposed in [Kennaway et.al.,1994], because
the length of the
reduction sequences is preserved by unraveling, and collapsing rules
are treated in a completely uniform way.
Università di Pisa
1997-07-16
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1979/1/TR-97-14.ps.gz
Corradini, Andrea and Drewes, Frank (1997) (Cyclic) Term Graph Rewriting is adequate for Rational Parallel Term Rewriting. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-14.ps.gz
oai:eprints.adm.unipi.it:1980
2015-01-23T10:13:06Z
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http://eprints.adm.unipi.it/1980/
Fast fraction-free triangularization of Bezoutians with applications to sub-resultant chain computation
Bini, D. A.
Gemignani, Luca
INF/01 - Informatica
An algorithm for the computation of the LU factorization over the
integers of an $n\times n$ Bezoutian $B$ is presented.
The algorithm requires $O(n^2)$ arithmetic operations and involves
integers having at most $O(n\log nc)$ bits, where $c$ is an upper
bound of the moduli
of the integer entries of $B$. As an application, by using the
correlations between Bezoutians and the Euclidean scheme, we devise a
new division-free algorithm for the computation of the polynomial
pseudo-remainder sequence of two polynomials of degree at most $n$ in
$O(n^2)$ arithmetic operations. The growth of the length of the
integers involved in the computation is kept at the minimum value,
i.e., $O(n\log nc)$ bits, no matter if the sequence is normal or not,
where $c$ is an upper bound of the moduli of the
input coefficients.
The algorithms, that rely on the Bareiss technique and on the
properties of the Schur complements of Bezoutians ,
improve the previous ones.
Università di Pisa
1997-09-05
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1980/1/TR-97-15.ps.gz
Bini, D. A. and Gemignani, Luca (1997) Fast fraction-free triangularization of Bezoutians with applications to sub-resultant chain computation. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-15.ps.gz
oai:eprints.adm.unipi.it:1981
2015-01-23T10:12:41Z
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74797065733D626F6F6B
http://eprints.adm.unipi.it/1981/
A Labelled Transition System for pi_epsilon-Calculus
van Breugel, Franck
INF/01 - Informatica
A labelled transition system is presented for Milner's
pi_epsilon-calculus. This system is related to the
reduction system for the calculus presented by Bellin
and Scott. Also a reduction system and a labelled
transition system for pi_epsilonI-calculus are given
and their correspondence is studied. This calculus is
a subcalculus of pi_epsilon-calculus in the way
Sangiorgi's piI-calculus is a subcalculus of ordinary
pi-calculus.
Università di Pisa
1997-09-09
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1981/1/TR-97-16.ps.gz
van Breugel, Franck (1997) A Labelled Transition System for pi_epsilon-Calculus. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-16.ps.gz
oai:eprints.adm.unipi.it:1982
2015-01-23T10:12:35Z
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74797065733D626F6F6B
http://eprints.adm.unipi.it/1982/
Active-U-Datalog: integrating active rules in a deductive database
Gervasi, Vincenzo
Raffaetà, Alessandra
INF/01 - Informatica
The marriage between logic programming and databases has given rise to
the definition of deductive databases. These systems allow the
users to express data manipulations and queries in a declarative way,
and permit efficient storage and retrieval of intensional knowledge.
Another improvement in the database field has come from the use of
active rules, linking the occurrence of certain events to a reaction
(e.g., updates of some data). This kind of rules has proven to be very
useful to ensure integrity constraints and to automatize common procedures.
This paper presents an integration of active rules in U-Datalog,
which is an extension to Datalog supporting declarative
specification of updates based on a nonimmediate update semantics.
The resulting language, called Active-U-Datalog, extends
the semantics of U-Datalog in a conservative way, introducing a
PARK-like semantics for active rules activation and firing, and for
handling conflicting update requests.
Università di Pisa
1997-07-15
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1982/1/TR-97-19.ps.gz
Gervasi, Vincenzo and Raffaetà, Alessandra (1997) Active-U-Datalog: integrating active rules in a deductive database. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-19.ps.gz
oai:eprints.adm.unipi.it:1983
2015-01-23T10:15:01Z
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74797065733D626F6F6B
http://eprints.adm.unipi.it/1983/
Failures, Finiteness, and Full Abstraction
van Breugel, Franck
INF/01 - Informatica
For a simple CCS-like language a trace semantics and a failure
semantics are presented. The failure semantics is shown to be
fully abstract with respect to the trace semantics if and only
if the set of internal actions is infinite.
Università di Pisa
1997-09-09
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1983/1/TR-97-18.ps.gz
van Breugel, Franck (1997) Failures, Finiteness, and Full Abstraction. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-18.ps.gz
oai:eprints.adm.unipi.it:1984
2015-01-23T10:14:47Z
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74797065733D626F6F6B
http://eprints.adm.unipi.it/1984/
Terminal Metric Spaces of Finitely Branching and Image Finite Linear processes
van Breugel, Franck
INF/01 - Informatica
Well-known metric spaces for modelling finitely branching and
image finite systems are shown to be (the carrier of) terminal
coalgebras.
Università di Pisa
1997-09-09
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1984/1/TR-97-17.ps.gz
van Breugel, Franck (1997) Terminal Metric Spaces of Finitely Branching and Image Finite Linear processes. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-17.ps.gz
oai:eprints.adm.unipi.it:1985
2015-01-23T10:14:17Z
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http://eprints.adm.unipi.it/1985/
Il monitoraggio dei contratti di grande rilievo
Ambriola, Vincenzo
Cignoni, Giovanni A.
INF/01 - Informatica
According to Italian law, monitoring is a kind of quality control that
must be performed during the carrying out of contracts regarding the
information systems of Italian Public Bodies. This technical report
describes and analyses monitoring as a tool to guarantee the quality of
software production and consequently to assure the customer's satisfaction.
It presents the institutional context in which monitoring is used,
its activities, its purposes, its areas of application, and
its relation to other kinds of quality control.
Università di Pisa
1997-09-30
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1985/1/TR-97-20.ps.gz
Ambriola, Vincenzo and Cignoni, Giovanni A. (1997) Il monitoraggio dei contratti di grande rilievo. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-20.ps.gz
oai:eprints.adm.unipi.it:1986
2015-01-23T10:14:05Z
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74797065733D626F6F6B
http://eprints.adm.unipi.it/1986/
On logic programs that do not fail
Pedreschi, Dino
Ruggieri, Salvatore
INF/01 - Informatica
This paper investigates the advantages of reasoning on logic
programs
and queries that have only successful derivations.
We consider an
extension of the logic programming paradigm that combines guarded
clauses, in the style of concurrent logic languages, and dynamic
selection rules. Some general conditions for a class of programs and
queries are stated, which characterize when successful
derivations only are present.
A few practical instances of the general conditions are
studied, and their applicability to real programs demonstrated.
The main contributions of the proposed method are: (i)
don't care non determinism can be safely adopted for programs
that do not fail,
(ii) termination of process networks
expressed as logic programs can be proved, by means of a simple proof
method developed for a fixed selection rule, and (iii) a strategy for
parallelizing terminating Prolog programs is identified.
Università di Pisa
1997-10-08
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1986/1/TR-97-21.ps.gz
Pedreschi, Dino and Ruggieri, Salvatore (1997) On logic programs that do not fail. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-21.ps.gz
oai:eprints.adm.unipi.it:1987
2015-01-23T10:16:01Z
7374617475733D707562
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74797065733D626F6F6B
http://eprints.adm.unipi.it/1987/
Making abstract interpretations complete
Giacobazzi, Roberto
Ranzato, Francesco
INF/01 - Informatica
Completeness in abstract interpretation is an ideal situation where
the abstract semantics is able to take full advantage of the power
of representation of the underlying abstract domain. Thus, complete
abstract interpretations can be rightfully considered as optimal.
In this article, we develop a general theory of completeness in
abstract interpretation, also dealing with the most frequent case of
least fixpoint semantics. We show that both completeness and least
fixpoint completeness are properties that only depend on the
underlying abstract domain. In this context, we demonstrate that
there always exist both the greatest complete and least fixpoint
complete restrictions of any abstract domain, and for continuous
semantic functions, the least complete extension exists as well.
Also, under certain hypotheses, a constructive characterization of
the least complete extensions and restrictions of abstract domains
is given as solutions of simple abstract domain equations. These
methodologies provide advanced algebraic tools for manipulating and
comparing abstract interpretations, which can be fruitfully used
both in program analysis and in semantics design. A number of
examples illustrating these techniques are given in the
fields of integer variable and logic program analysis.
Università di Pisa
1997-11-03
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1987/1/TR-97-22.ps.gz
Giacobazzi, Roberto and Ranzato, Francesco (1997) Making abstract interpretations complete. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-22.ps.gz
oai:eprints.adm.unipi.it:1988
2015-01-23T10:15:14Z
7374617475733D707562
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http://eprints.adm.unipi.it/1988/
Masked Interval Routing: a New Routing Scheme
Luccio, Fabrizio
Mahafzah, M.
Omari, M.
Pagli, Linda
INF/01 - Informatica
We introduce the new Masked Interval Routing Scheme, MIRS for short, where
a maskis added to each interval to indicate particular subsets of
"consecutive" labels. Interval routing becomes more flexible,
with the classical IRS scheme being a special case of MIRS.
We then take two directions. First we show that the interval information
stored in the network may be drastically reduced in the hard cases, proving
that in globe graphs of O(n^2) vertices the number of intervals per edge
goes down from
Omega(n) to O(log n). The technique is then extended to globe graphs
of arbitrary dimensions. Second we show that MIRS may be advantageously used in
fault-tolerant networks, proving that optimal routing with one interval
per edge is still possible in hypercubes with a "harmless" subset of faulty
vertices.
This work is aimed to introducing a new technique. Further research is
needed in both the directions taken here. Still, the examples provided
show that MIRS may be useful in practical applications.
Università di Pisa
1997-12-05
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1988/1/TR-97-23.ps.gz
Luccio, Fabrizio and Mahafzah, M. and Omari, M. and Pagli, Linda (1997) Masked Interval Routing: a New Routing Scheme. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-23.ps.gz
oai:eprints.adm.unipi.it:1989
2015-01-26T13:30:43Z
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74797065733D626F6F6B
http://eprints.adm.unipi.it/1989/
A Logic-Based Calculus of Fluents
Brandano, S.
INF/01 - Informatica
This report formally defines the class of all problems on {\em
Reasoning about Actions and Change}, where accurate and complete
information about actions, together with strict inertia in continuous
time, continuous change and alternative results of possibly
concurrent and independent actions are the assumed properties. The
intended model set for each member in the class is defined in terms
of a model-theoretic trajectory semantics. The case is designated, in
the {\em Features and Fluents} framework, with the~\KRACi family of
reasoning problems. A fix-point characterization of the subclass
\KspRAdCi is then given in terms of a simulative algebraic semantics,
and show which are the difficulties when approaching the full class
with that method. A non-simulative algebraic semantics is then
presented as an alternative algebraic characterization of the
model-theoretic trajectory semantics. Still the characterization is
made in terms of complete lattices and continuous operators on those
complete lattices. The algebraic semantics is shown to be correct and
complete with respect to the trajectory-semantics, when applied to
reasoning problems in \KRACi. Finally, adopting the non-simulative
algebraic semantics as proof procedure, a logic-based {\em
Calculus~of~Fluents} is defined, via a meta-theoretic extension of
the Horn Clause Logic using the non-ground representation of object
level variables. The meta-interpreter consists in the Horn clause
representation of the proof procedure. The calculus is shown to be
decidable, domain independent and class dependent; its semantics
consists in the non-simulative algebraic semantics, and is executable
as a logic program by the SLD-resolution rule.
Università di Pisa
1998-01-12
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1989/1/TR-98-01.ps.gz
Brandano, S. (1998) A Logic-Based Calculus of Fluents. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-98-01.ps.gz
oai:eprints.adm.unipi.it:1990
2015-01-23T10:16:33Z
7374617475733D707562
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http://eprints.adm.unipi.it/1990/
Motivazioni comportamentali e insiemi attrattivi nei modelli stocastici per il trasporto collettivo
Paiano, Pietro
Pallottino, Stefano
INF/01 - Informatica
In un recente lavoro [13] e` stato proposto un modello di tipo logit
gerarchico per l'assegnazione dei flussi ad una rete di trasporto collettivo
urbano. Nel modello viene ipotizzato, su alcune ipotesi comportamentali dei
passeggeri, che ad ogni fermata e per ogni destinazione venga considerato
come attivo al piu` un iperarco di salita.
In questo lavoro, dopo un'introduzione al modello logit di Dial [6] volta
a mostrare come per il trasporto privato un modello logit di tipo globale
coincide con un modello gerarchico, viene analizzato il modello proposto in
[13] e vengono formulate ipotesi alternative di comportamento dei passeggeri
che implicano la possibile presenza di piu` iperarchi attivi alla medesima
fermata per la medesima destinazione. Viene quindi proposta una tecnica di
risoluzione del modello, piu` generale di quella descritta in [13], e
vengono mostrati gli effetti delle diverse ipotesi su alcuni casi test.
Università di Pisa
1997-05-22
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1990/1/TR-97-09.ps.gz
Paiano, Pietro and Pallottino, Stefano (1997) Motivazioni comportamentali e insiemi attrattivi nei modelli stocastici per il trasporto collettivo. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-97-09.ps.gz
oai:eprints.adm.unipi.it:1991
2015-01-23T10:16:17Z
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http://eprints.adm.unipi.it/1991/
$\exists$-universal termination of logic programs
Ruggieri, Salvatore
INF/01 - Informatica
We introduce the notion of $\exists$-universal termination of logic
programs. A program P and a goal G $\exists$-universally
terminate iff there exists a selection rule S such that every
SLD-derivation of P U { G }$via S is finite.
We claim that it is an essential concept for declarative
programming, where a crucial point is to associate a
terminating control strategy to programs and goals.
We show that $\exists$-universal termination and universal termination
via fair selection rules coincide. Then we offer a characterization of
$\exists$-universal termination by defining fair-bounded programs
and goals. They provide us with a correct and complete method
of proving $\exists$-universal termination. We show other valuable
properties of fair-bounded programs and goals, including persistency,
modularity, ease of use in paper & pencil proofs,
automatization of proofs.
Università di Pisa
1998-01-26
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1991/1/TR-98-02.ps.gz
Ruggieri, Salvatore (1998) $\exists$-universal termination of logic programs. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-98-02.ps.gz
oai:eprints.adm.unipi.it:1992
2015-01-26T13:31:39Z
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http://eprints.adm.unipi.it/1992/
Towards a Fluent Logic Programming
Pallotta, Vincenzo
Turini, Franco
INF/01 - Informatica
This work involves two areas of research in computer science, namely
Knowledge Representation and Logic Programming. Starting from the
formalism proposed in Features Fluents by Erik Sandewall
for describing and reasoning about Inhabited Dynamical Systems, we
try to reconstruct it within a Logic Programming framework. The result
is an extended logic programming language called Fluent Logic
Programming (FLP) capable to deal with the main issues
of the frame problem, in the context of Reasoning about
Action and Change. From one point of view, FLP is the reconstruction
of the proof-theory for the Sandewall's Discrete Fluent Logic
by means of Meta-Logic Programming, on the other it is an attempt
to integrate Temporal Reasoning and Logic Programming. In order to
show soundness and completeness results between the Underlying
Semantics and the Meta-Logical Semantics on which FLP is based,
we provide a new abstract semantics for FLP as a bridge between them.
Università di Pisa
1998-03-09
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1992/1/TR-98-03.ps.gz
Pallotta, Vincenzo and Turini, Franco (1998) Towards a Fluent Logic Programming. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-98-03.ps.gz
oai:eprints.adm.unipi.it:1993
2015-01-26T13:31:33Z
7374617475733D707562
7375626A656374733D417265613031:494E462F3031
74797065733D626F6F6B
http://eprints.adm.unipi.it/1993/
Generalized Bundle Methods
Frangioni, Antonio
INF/01 - Informatica
We propose a class of generalized Bundle methods where the stabilizi=
term can be any closed convex function satisfying certain properties. =
We prove finite termination, asymptotic convergence and finite convergenc=
e to an optimal point of different variants of the algorithm: for some of=
these proofs, f-regularity of the function (a new generalization of inf-=
compactness) is required. Our analysis gives a unified convergence proof =
for several classes of Bundle methods that have been so far regarded as d=
istinct, enhancing on the results known for some of them: furthermore, it=
covers methods proposed in the literature that had not previously been r=
ecognised as Bundle methods. A novelty in our approach is the proposal of=
a dual for the minimization problem: we show that Bundle methods can be =
seen as a dual ascent approach to one single nonlinear problem in the dua=
l space, where nonlinear subproblems are approximately solved at each ste=
p with an inner linearization approach. This interpretation is particular=
ly
Università di Pisa
1998-03-17
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1993/1/TR-98-04.ps.gz
Frangioni, Antonio (1998) Generalized Bundle Methods. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-98-04.ps.gz
oai:eprints.adm.unipi.it:1994
2015-01-26T13:30:52Z
7374617475733D707562
7375626A656374733D417265613031:494E462F3031
74797065733D626F6F6B
http://eprints.adm.unipi.it/1994/
Rewriting on cyclic structures
Corradini, Andrea
Gadducci, Fabio
INF/01 - Informatica
We present a categorical formulation
of the rewriting of possibly cyclic term graphs, and the proof
that this presentation is equivalent to the well-accepted
operational definition proposed by Barendregt et al., but for the
case of circular redexes, for which we propose (and
justify formally) a different treatment.
The categorical framework,
based on suitable 2-categories, allows to model also
automatic garbage
collection and rules for sharing/unsharing and
folding/unfolding of structures.
Furthermore, it can be used for defining various extensions of
term graph rewriting, and for relating it to other
rewriting formalisms.
Università di Pisa
1998-06-12
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1994/1/TR-98-05.ps.gz
Corradini, Andrea and Gadducci, Fabio (1998) Rewriting on cyclic structures. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-98-05.ps.gz
oai:eprints.adm.unipi.it:1995
2015-01-26T13:30:31Z
7374617475733D707562
7375626A656374733D417265613031:494E462F3031
74797065733D626F6F6B
http://eprints.adm.unipi.it/1995/
Routing with Minimum Fragmentation Cost
Gallo, Giorgio
Scaparra, Maria Paola
INF/01 - Informatica
One of the greatest difficulties involved in communication networks
project is the need to interconnect different networks to form a
unique internetwork. A major headache is the differing maximum packet
sizes allowed by each network, which causes oversize packets to be
broken up into appropriately sized fragments. Unfortunately, the
fragmentation process implies additional costs, tightly bounded up
with routing and fragmentation strategies in use. The approach commonly
used in IP protocols provides two separated functions which operate in
a completely indipendent way. This adversely affects network performance
measures, both quantitatively (throughput) and qualitatively (average
packet delay), whereas some form of cooperation between the two functions
could result in a reduction of this efficiency loss. This paper presents
a pseudo-polynomial algorithm for solving the combined fragmentation
and routing problem. The method of solution is based on the concept of
bicriterion shortest path problem, where two distinct objective functions
must be minimized: the path length (in accordance with many classic
routing algorithm) and the number of fragments received by the
destination host. Besides, the paper deals with the problem of the
effective fragments-hops minimization. An algorithm aimed at this
purpose is provided together with the analysis of the possibility to
reduce its running time under appropriate considerations on the
generated fragment sizes.
Università di Pisa
1998-06-26
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1995/1/TR-98-06.ps.gz
Gallo, Giorgio and Scaparra, Maria Paola (1998) Routing with Minimum Fragmentation Cost. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-98-06.ps.gz
oai:eprints.adm.unipi.it:1996
2015-01-26T13:32:15Z
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7375626A656374733D417265613031:494E462F3031
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http://eprints.adm.unipi.it/1996/
The YALL language
Cisternino, Antonio
Laganà, Maria Rita
INF/01 - Informatica
The authors of Logo wanted to create a tool to help children build
and explore the world of programming as means of building and exploring
their own logical thought. The strength of this idea is particular and
the turtle has carried his work out well. Today, however, new programming
paradigms call for new metaphors and the technological gap between the
turtle and modern graphic and multimedia programs seems to make less
powerful the original Logo metaphor. In this paper we propose to enhance
standard Logo by introducing modern program paradigms. In particular we
extend Logo with object-oriented programming and multi-agent programming
features. This new language is called YALL and try to change the way of
programming Logo without abandon the original philosophy of the language.
We introduce a new approach to express the inheritance relation that is
more suitable for children. We discuss about these new extensions to Logo
describing the new commands introduced. We also discuss a possible
implementation of YALL using the Java language by Sun Microsystems.
Università di Pisa
1998-07-02
Book
NonPeerReviewed
application/postscript
en
cc_by_nd
http://eprints.adm.unipi.it/1996/1/TR-98-07.ps.gz
Cisternino, Antonio and Laganà, Maria Rita (1998) The YALL language. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.
http://compass2.di.unipi.it/TR/files/TR-98-07.ps.gz
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