Logics in Computer Science: A Study on Extensions of Temporal and Strategic Logics PDF
Preview Logics in Computer Science: A Study on Extensions of Temporal and Strategic Logics
Atlantis Studies in Computing Series Editors: J. Bergstra · M. Mislove Fabio Mogavero Logics in Computer Science A Study on Extensions of Temporal and Strategic Logics Atlantis Studies in Computing Volume 3 Series Editors Jan A. Bergstra, University of Amsterdam, Amsterdam, The Netherlands Michael W. Mislove, Tulane University, New Orleans, USA For furthervolumes: www.atlantis-press.com Aims and Scope of the Series The series aims at publishing books in the areas of computer science, computer andnetworktechnology,ITmanagement,informationtechnologyandinformatics from the technological, managerial, theoretical/fundamental, social or historical perspective. We welcome books in the following categories: Technical monographs: these will be reviewed as to timeliness, usefulness, rele- vance, completeness and clarity of presentation. Textbooks. Books of a more speculative nature: these will be reviewed as to relevance and clarity of presentation. For more information on this series and our other book series, please visit our website at: www.atlantis-press.com/publications/books Atlantis Press 29, avenue Laumière 75019 Paris, France Fabio Mogavero Logics in Computer Science A Study on Extensions of Temporal and Strategic Logics FabioMogavero Università degli StudidiNapoliFederico II Napoli Italy ISSN 2212-8557 ISSN 2212-8565 (electronic) ISBN 978-94-91216-94-7 ISBN 978-94-91216-95-4 (eBook) DOI 10.2991/978-94-91216-95-4 LibraryofCongressControlNumber:2013938748 (cid:2)AtlantisPressandtheauthors2013 Thisbook,oranypartsthereof,maynotbereproducedforcommercialpurposesinanyformorbyany means, electronic or mechanical, including photocopying, recording or any information storage and retrievalsystemknownortobeinvented,withoutpriorpermissionfromthePublisher. Printedonacid-freepaper To Antonella, my gentle love To my parents and grandparents ‘‘Thought is only a flash between two long nights, but this flash is everything.’’ Henri Poincare Foreword TheItalianchapteroftheEuropeanAssociationforTheoreticalComputerScience (EATCS)wasfoundedin1988,andaimsatfacilitatingtheexchangeofideasand resultsamongItaliantheoreticalcomputerscientists,andatstimulatingcooperation betweenthe theoretical andthe applied communities inItaly. One of the major activities of this chapter isto promoteresearch in theoretical computerscience,stimulatingscientificexcellencebysupportingandencouraging the very best and creative young Italian theoretical computer scientists. This is done also by sponsoring a prize for the best Ph.D. thesis. This award has been usually presented every two years and an interdisciplinary committee selects the besttwoPh.D.theses,amongthosedefendedintheprevioustwo-yearperiod,one on the themes of Algorithms, Automata, Complexity and Game Theory, and the other on the themes of Logics, Semantics and Programming Theory. In 2012 we started a cooperation with Atlantis Press so that the selected Ph.D. theses would be published as volumes in the Atlantis Studies in Computing. The present volume contains one of the two theses selected for publication in 2012: Logics in Computer Science by Fabio Mogavero (supervisor: Prof. Aniello Murano, University of Napoli Federico II, Napoli, Italy) and On Searching and Extracting Strings from Compressed Textual Data by Ros- sano Venturini (supervisor: Prof. Paolo Ferragina, University of Pisa, Italy). The scientific committee which selected these theses was composed of Pro- fessorsMarcellaAnselmo(UniversityofSalerno),PierluigiCrescenzi(University of Florence) and Gianluigi Zavattaro (University of Bologna). They gave the following reasons to justify the assignment of the award to the thesis by Fabio Mogavero ‘‘The thesis by Fabio Mogavero addresses problems related to property spec- ification and verification by means of temporal logics and model checking. Inparticular,thisworksignificantlycontributestotwospecificfields:temporal logics with graded modalities, as far as closed systems are concerned, and logics for strategies, as far as concurrent and multi-agent systems are concerned. Gradedmodalitiesareparticularlyusefultoexpresspropertieslike:‘‘thereare atleastndifferentcomputationsallowingthesystemtoreachapredefinedstate’’. vii viii Foreword Concerningthissubject,themaincontributionofthethesisisGCTL:anextension of the Computation Tree Logic (CTL) with such operators. The study of suc- cinctness and complexity of satisfiability for GCTL is particularly valuable: sat- isfiabilityturnsouttobeanEXPTIME-COMPLETEproblem,asitisthecaseforother logics with graded modalities in the literature, while GCTL is proved to be exponentially more succinct with respect to those logics. The logics for strategies have been proposed in the literature as tools to deal withinteractionsinopensystems.Aboutthissubject,themaincontributionofthis thesis is SL, a logic particularly useful to reason about multi-agent concurrent systems. SL strictly includes other similar logics such as the strategy logic in the literature, like the strategy logic by Chatterjee-Henzinger-Piterman. The model checking problem is proved to be 2EXPTIME-COMPLETE for SL, a result that sig- nificantly improves the complexity boundaries already known for the logic by Chatterjee-Henzinger-Piterman. Theaboveresultshavebeenpresentedatconferencesofexcellentinternational level like the Symposium on Logic in Computer Science (LICS) and the Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS).’’ ThisyeartheItalianchapterofEATCSdecidedtodedicatethetwoprizestothe memoryofProf.StefanoVarricchio(theoneonthemesofAlgorithms,Automata, Complexity and Game Theory), and Prof. Nadia Busi (the one on themes on Logics, Semantics and Programming Theory), both excellent researchers who prematurely passed away. I hope that this initiative will further contribute to strengthen the sense of belongingtothesamecommunityofalltheyoungresearcherswhohaveaccepted the challenges posed by any branch of theoretical computer science. Napoli, January 2013 Tiziana Calamoneri Preface For a supervisor, it is always a pleasure and an honor to write a foreword for the thesis of his Ph.D. student. For an excellent student like Fabio, this becomes enormously great. Rather than talking about the remarkable results obtained by Fabio, which are absolutely well introduced and described in this thesis, I would like to talk about passion, tenacity, perseverance, and above all the difficulty that Fabio had to overcome in obtaining them. Also, I would love to report how everything began and some anecdotes, which I am sure, one day, by reading them here again, will give a remembrance of the good time we spent all together during the Ph.D. period. Moreover, I would like to mention some of the people who had a signif- icant role along Fabio’s scientific training. IstillrememberthefirsttimeImetFabio.Itwastheendof2006.Fabiotoldme ofhispassionfortheformalmethods,inparticularmodalandtemporallogics,the several booksandarticleshehadread,and hiswilltodoaMaster thesis onthese topics. I must admit that I was surprised and a little bit puzzled to see an engi- neeringstudentinterestedinsuchtopicsandaskingacomputerscienceresearcher to be his thesis advisor. At the same time I was happy, because during the years spent at the computer science course, I had never seen a student of mine with the same true interests. At that time, I had just finished a tough work on mu-calculus enriched with graded and backwards modalities. I spoke to Fabio and mentioned to him the possibility of extending the same work to branching-time temporal logics. For a week, Fabio came back to me with a series of comments on my work and a first clearformalizationofGradedComputationTreeLogicwithbackwardsmodalities. It was at that moment that I got fully convinced that Fabio could easily attend a Ph.D.programandachievehighlevelresults.ThefirstaimwastofinishhisMaster thesis in time for the Ph.D. call, that is, within October 2007, but without letting the Master thesis to suffer in quality. We achieved the time target by a whisker! FabiodiscussedhisMasterthesisattheendofOctoberand,mostimportant,hegot a special encomium from the board that led me to be very proud of all the work done. Then, Fabio participated in the Ph.D. examination and got the best score. Thus, we immediately started the doctoral program. We decided together local ix x Preface coursesandsummerschoolstoattend.Mainly,weimmediatelywentbacktowork on the topics of research undertaken during the Master’s thesis and thanks to important new results, we wrote two articles, one on Graded Computation Tree Logic (GCTL, for short) and the other on Minimal Model Quantifiers. Both have requiredalotofeffortthathasoftenledustoworkwithoutinterruptionforweeks (Sundaysincluded).Theresultshavebeenverysatisfactoryandafteraboutayear both works have been published in conference proceedings. In particular the resultsonGCTLwerepresentedattheoutstandingconferenceLICS2009byFabio, in the United States of America. Meanwhile, I have to mention that, at the same Ph.D. competition that Fabio took, another engineering student participated and won: Alessandro Bianco. Immediately after the competition, Alessandro joined our group, working under mysupervisionaswell.ItwasFabiowhoencouragedandpersuadedAlessandroto participateinthePh.D.competitionandwithpleasureIcansaythathispresencein the laboratory has been a great enrichment for the entire group. In this, Fabio has proved to be an excellent talent scout. Fabio has been a sincere friend toward Alessandroandalwaysspurredhimontheresearchactivity.Itwasagreatpleasure togetinthelabandseethemdiscussdeeplyonresearchtopicsofanysort.Inthree years, we achieved many important results together with Alessandro but, unfor- tunately, many of them did not find space in this thesis. I think that period would not have been the same without having Alessandro with us. I promised at the beginning some anecdotes. Well, here they are. Mostly, they are related with Fabio’s traveling. Let me say that every trip Fabio has taken duringhisPh.D.,beitaschool,aconference,oravisitingresearcherperiod,there has always been something disastrous: a flood, a train trip canceled, an airplane that would have changed the landing airport at the very last moment, to mention justafew.Forexample,thefirstschoolFabioattendedwasinGermany.Whilehe was moving from the school location to the hotel, a deluge fell on Fabio, without giving him any opportunity of covering. The second school was in Italy, at Ber- tinoro, the return home was an odyssey because of a train crash. But, my favorite stories are related to the four months spent by Fabio as a visiting scholar in Houston tovisitMoshe Vardiat RiceUniversity,inthe Autumnof2008.Well,it wasmewhopushedFabiotovisitMoshe.Overall,IvisitedMosheformorethana year during my Ph.D. and I enjoyed very much my stay there. On the contrary, Fabio’svisitingstayhasbeenfullofadventure,startingwiththeoutgoingjourney: duetoaviolentstorminHouston,theairplanehadtofinallylandinDallas.After about a month of permanence in Houston, a violent hurricane came and swept away half of the city. Most of the population remained without electricity for almost a month with all the difficulties that could arise, and so it happened for Fabio. You can imagine my apprehension being in Italy! Well, at the end Fabio returned to Italy 17 pounds lighter, but with a formidable research idea: a new Strategy Logic (SL, for short)! At least the research goal was achieved. At Rice, Moshe first introduced Fabio to the logics for strategic reasoning throughATL*,thenhesuggestedhimtoinvestigatethislogicalongwithsomesort ofextensions,includingthepastmodalitiesandtheconceptofrelentfulness.Then,
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