[Programming Languages] Formal Definitions and Theory—Semantics General Terms
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CompositionalFailure-basedSemanticEquivalencesfor
ReoSpecifications
MohammadIzadi
DepartmentofComputerEngineering
sharifUniversityofTechnology
Tehran,Iranizadi@ce.sharif.eduAliMovaghar
DepartmentofComputerEngineering
sharifUniversityofTechnology
Tehran,Iranmovaghar@sharif.edu
ABSTRACT
Reoisacoordinationlanguageformodelingcomponentcon-
nectorsofcomponent-basedcomputingsystems.Weshow
thatthefailure-basedequivalencesNDFDandCFFDare
congruenceswithrespecttocompositionoperatorsofReo.
CategoriesandSubjectDescriptors
D.2.4[SoftwareEngineering]:Software/ProgramVerifi-
cation—Languages;F.4.3[MathematicalLogicandFor-
malLanguages]:FormalLanguages—Verification;D.3.1
[ProgrammingLanguages]:FormalDefinitionsandThe-
ory—Semantics
GeneralTerms
Languages,Semantics,Verification.
Keywords
ReoSpecificationLanguage,ConstraintAutomata,Failure-
basedEquivalences,Coordination,Component-basedSys-
tems,Semantics.
1.EXTENDEDABSTRACT
Theconceptofcomponentbasedsystems,especiallycom-
ponentbasedsoftware,isaphilosophyorwayofthinking
todealwiththecomplexityindesigninglargescalecom-
putingsystems.Oneofthemaingoalsofthisapproachis
tocomposereusablecomponentsbysomegluecodes.The
modelorthewayinwhichthesecomponentsarecomposed
iscalledcoordinationmodel.Sometimestherearesomefor-
malorprogramminglanguageswhichareusedforspecifica-
tionofcoordinationmodels.Suchlanguagesarecalledas
coordinationlanguages.Reo,asoneofthemostrecently
proposedcoordinationlanguages,isachannelbasedexoge-
nouscoordinationlanguageinwhichcomplexcoordinators
arecompositionallybuiltoutofsimplerones[1,2,3].By
usingReospecifications,complexcomponentconnectorscan
Permissiontomakedigitalorhardcopiesofallorpartofthisworkforpersonalorclassroomuseisgrantedwithoutfeeprovidedthatcopiesarenotmadeordistributedforprofitorcommercialadvantageandthatcopiesbearthisnoticeandthefullcitationonthefirstpage.Tocopyotherwise,torepublish,topostonserversortoredistributetolists,requirespriorspecificpermissionand/orafee.SixthInternationalWorkshoponSpecificationandVerificationofComponent-BasedSystems(SAVCBS2007),September3-4,2007,CavtatnearDubrovnik,Croatia.Copyright2007ACMISBN978-1-59593-721-6/07/0009...$5.00.beorganizedinanetworkofchannelsandbuildinacom-
positionalmanner.Reoreliesonaveryliberalandsimple
notionofchannelsandcanmodelanykindofpeer-to-peer
communication.ThechannelsusedinReonetworkscanbe
consideredassimplecommunicatingprocessesandtheonly
requirementsforthemarethatchannelsshouldhavetwo
ends(orI/Ointerfaces),declaredtobesinkorsourceends,
andauser-definedsemantics.Atsourceendsdataitems
enterthechannelbyperformingcorrespondingwriteopera-
tions.Dataitemsarereceivedfromachannelatsinkends
byperformingcorrespondingreadoperations.Reoallows
foranopenendedsetofchanneltypeswithuserdefined
semantics.
Ifwewanttobeabletoreasonaboutpropertiesofspec-
ificationsorverifytheircorrectness,Reo,aswellasany
otherprocessspecificationlanguages,shouldbegivenab-
stractsemantics.Thekeyquestioningivingasemantic
modeltoaspecificationlanguageis:”Whenevercanwesay
thattwospecificationsortwomodelsareequivalent?”Nu-
merousdefinitionsofdifferentequivalence-relationsfortran-
sitionsystembasedmodelshavebeenpresentedintheliter-
ature.Traceequivalence(automata-theoreticequivalence),
weakbisimilaritypresentedbyMilner[9]andfailure-based
equivalences(CSP-likeequivalences)suchastheequivalence
presentedbyHoare[7]areexamplesoftheseequivalences.
Constraintautomaton,asanextensionoffiniteorB¨uchi
automaton,isaformalismproposedtocapturetheoper-
ationalsemanticsofReo[4].Inaconstraintautomaton,
contrarytofiniteautomataandlabeledtransitionsystems,
thelabelofatransitionisnotasimplecharacteroraction
name.Atransitionlabelcontainsasetofnamesanda(con-
straint)proposition.Thesetofnamesindicatesthenames
ofportswhichareparticipantindoingthetransitionand
thepropositionexpressessomeconstraintaboutthedataof
theports.
Inthispresentation,weareinterestedtoinvestigatefailure-
basedequivalencesforconstraintautomataastheabstract
semanticsofReoandtheircongruencywithrespecttocom-
positionoperatorswhichareusefulincomposingReospec-
ifications.Theultimategoalistoprepareanenvironment
forcompositionalmodelcheckingofReospecificationsus-
ingequivalencebasedreductionmethod.Inthismethod,the
modelsofcomponentsandconnectorsofacomponent-based
systemarereducedwithrespecttoanequivalencerelation
beforebuildingthemodelofthecompletesystem[5,6].An
equivalencerelationshouldhavetwopropertiesinorderto
beusefulintheequivalencebasedcompositionalreduction
method:itshouldpreservetheclassofpropertiestobever-
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