Table Of ContentMathias Soeken · Rolf Drechsler
Formal
Specifi cation
Level
Concepts, Methods, and Algorithms
Formal Specification Level
Mathias Soeken • Rolf Drechsler
Formal Specification Level
Concepts, Methods, and Algorithms
123
MathiasSoeken RolfDrechsler
UniversityofBremen/DFKI UniversityofBremen/DFKI
Bremen,Germany Bremen,Germany
ISBN978-3-319-08698-9 ISBN978-3-319-08699-6(eBook)
DOI10.1007/978-3-319-08699-6
SpringerChamHeidelbergNewYorkDordrechtLondon
LibraryofCongressControlNumber:2014952327
©SpringerInternationalPublishingSwitzerland2015
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Preface
This book addresses the important problem of formal verification at the very first
stage of the design flow for complex hardware and software systems. System
designers are interested in finding bugs as early as possible in the design flow in
order to meet strict and important time-to-market constraints. However, the initial
system description is usually provided in terms of textual specifications which do
notdirectlyallowtheapplicationofformalverificationtools.Thusfar,thefirstpoint
for some formal analyses appears during the implementation phase; however, lots
ofefforthavebeenspentuntilthatpoint.
Two major contributions are provided in this book to solve this problem which
have been united in a new abstraction level, called the Formal Specification Level
for modern design flows: (i) algorithms based on natural language processing
techniques are proposed that help to automatize the extraction of formal models
from textual specifications, and (ii) verification techniques are introduced that
allow formal verification on these extracted formal models. Since implementation
detailsareyetnotavailableintheseformalmodels,theverificationmethodstarget
conceptual consistency of the specifications and can, e.g., find implementation-
independentcontradictions.
Thebooksummarizesmanyresearchresultsthatwereachievedinthelast4years
intheGroupofComputerArchitecture,UniversityofBremen,mainlyinthecontext
ofthefirstauthor’sPh.D.studies.Thisbookwouldnothavebeenpossiblewithout
thehelpofourcollaborators,inparticularRobertWille,whohasbeenaninvaluable
partner in carrying out many interesting research ideas. Furthermore, we wish to
thank Melanie Diepenbeck and Julia Seiter for their additional valuable feedback.
WealsowishtothankEstherGuerraforhersupportasexternalexaminerandforher
timeandherconstructivecommentsandsuggestions.SpecialthanksalsotoNabila
Abdessaied, Stefan Frehse, Stefan Göller, Daniel Große, Oliver Keszöcze, Hoang
M.Le,andHeinzRienerforthecountlessinterestingdiscussions.
v
vi Preface
A large part of the work that has been presented in this book has been
developed within a Reinhart Koselleck project funded by the German Research
Foundation (DFG) (DR 287/23-1) and in the SPECifIC project funded by the
FederalMinistryofEducationandResearch(BMBF)(01IW13001).
Bremen,Germany MathiasSoeken
August2014 RolfDrechsler
Contents
1 Introduction .................................................................. 1
2 Background................................................................... 7
2.1 ModelsandSystemStates.............................................. 7
2.1.1 TypeSystem .................................................... 8
2.1.2 Models .......................................................... 10
2.2 ObjectConstraintLanguage............................................ 12
2.2.1 ConstraintExpressions ......................................... 12
2.2.2 QueryExpressions.............................................. 13
2.3 BooleanSatisfiability ................................................... 14
2.4 NaturalLanguageProcessing........................................... 17
2.4.1 Part-of-SpeechTagging......................................... 18
2.4.2 PhraseStructureTrees.......................................... 18
2.4.3 TypedDependencies............................................ 19
2.4.4 WordNet......................................................... 21
3 NLP-AssistedModelGeneration........................................... 23
3.1 StructureExtraction..................................................... 24
3.1.1 ClassesandActors.............................................. 24
3.1.2 Attributes........................................................ 28
3.1.3 Operations....................................................... 32
3.1.4 Associations..................................................... 34
3.1.5 ExtractingModelsfromtheDatabase ......................... 36
3.2 ExpressionExtraction................................................... 36
3.2.1 Implementation ................................................. 38
3.2.2 Discussion....................................................... 44
3.3 IntegratedDevelopmentEnvironment ................................. 45
3.4 EvaluatingExamples.................................................... 48
3.4.1 StructureExtraction ............................................ 50
3.4.2 ExpressionExtraction .......................................... 52
3.5 AssistedBehaviorDrivenDevelopment ............................... 54
3.6 Summary ................................................................ 54
vii
viii Contents
4 VerificationofStaticAspects ............................................... 57
4.1 StaticAspectsofModels ............................................... 58
4.2 ModelFinder............................................................ 62
4.2.1 USESnapshotGenerator....................................... 62
4.2.2 Alloy............................................................. 64
4.2.3 SATModuloTheories.......................................... 68
4.3 Transformation.......................................................... 71
4.3.1 TransformationofAttributes................................... 72
4.3.2 TransformationofLinks........................................ 73
4.3.3 TransformationofOCLConstraints........................... 76
4.3.4 TransformationofOCLCollectionTypes..................... 87
4.4 VerificationTasks ....................................................... 95
4.5 DeterminationofProblemBounds..................................... 96
4.5.1 DynamicProblemBounds ..................................... 96
4.5.2 AutomaticDeterminationofProblemBounds ................ 97
4.6 DebuggingofInconsistentModels..................................... 102
4.6.1 GeneralDebuggingFlow....................................... 104
4.6.2 DebuggingMethods............................................ 104
4.7 TestGenerationforModelTransformations........................... 107
4.8 Summary ................................................................ 108
5 VerificationofDynamicAspects............................................ 109
5.1 DynamicAspectsofModels............................................ 111
5.2 TransformationofOperationCalls..................................... 115
5.3 VerificationTasks ....................................................... 117
5.3.1 ExecutionSemantics............................................ 119
5.4 CaseStudy:InvariantElimination...................................... 121
5.4.1 ProblemFormulation........................................... 122
5.4.2 Implementation ................................................. 124
5.4.3 Evaluation....................................................... 125
5.5 Summary ................................................................ 128
6 Conclusions................................................................... 131
References......................................................................... 133
Index............................................................................... 137
Chapter 1
Introduction
Noteverythingthatcanbecountedcounts,andnoteverythingthatcountscanbecounted.
—WilliamB.Cameron,InformalSociology(1963)
Being composed of up to several billion components, the design of embedded
systemsisoneofthemostcomplexproblemspeoplearefacingtoday.Whileitwas
possible to fully design such systems gate by gate on the drawing table 40 years
ago, this procedure has become intractable due to the ever increasing complexity.
Inordertomasterthedevelopmentofsuchcomplexhardwareandsoftwaresystems,
researchershavecomeupwithasophisticateddesignflowoverthelastdecadesthat
consistsofseverallevelsofabstractionstartingfromanaturallanguagespecification
andresultinginaflattenedtransistornetlistwithpreciselayoutinformation.
Today, a design flow as illustrated in Fig.1.1a is applied. The initial starting
point and therefore the most abstract description is given by means of a natural
language specification. However, in order to perform even the simplest automatic
synthesis techniques, a formal representation of this specification is required.
For this purpose, an initial implementation is generated at the Electronic System
Level(ESL)[51]usinghigh-levelprogramminglanguagessuchasSystemC,aC++
class library for event driven simulation of concurrent processes. This system
level description enables the execution and simulation of the desired design, but
still hides details concerning a precise realization in both hardware and software.
Fromthisdescription,thesystemmodelisconsecutivelyrefinedinsuccessivesteps
leading to descriptions at the Register Transfer Level (RTL), the gate level, and
thephysicallevel.Attheendofthisprocess,theresultingsystemissenttoachip
manufacturer.
As embedded systems are often employed in safety critical systems such as
avionic, automotive, and medical applications, ensuring the correctness is of high
importance. For this purpose, usually each transformation from one abstraction
level to the next refinement is checked for equivalence. But due to the absence
ofaformaldescriptionatthespecification level,automaticverificationtechniques
are not applicable for the comparison with the system level. The gap between the
©SpringerInternationalPublishingSwitzerland2015 1
M.Soeken,R.Drechsler,FormalSpecificationLevel,
DOI10.1007/978-3-319-08699-6__1
