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A Static Approach to Consistency Verification of UML Models

Andrea Baruzzo abaruzzo@computer.org Department of Computer Science University of Udine. A Static Approach to Consistency Verification of UML Models. MoDeV 2 a 2006 Workshop. Agenda. The context The problems to address The goals The method

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A Static Approach to Consistency Verification of UML Models

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  1. Andrea Baruzzo abaruzzo@computer.org Department of Computer Science University of Udine A Static Approach to Consistency Verification of UML Models MoDeV2a 2006 Workshop

  2. Agenda • The context • The problems to address • The goals • The method • The method at work • Future works

  3. Requirements Consistency Correctness model precision Models Code The Context • Model-Driven Development • Model elaboration (possibly manual but typically automatic) • Build the right model! …early validation! • Model-Driven Architecture development [Mellor, Warmer, OMG] • UML alone is not enough precise to build software and to verify it • The need of a formal specification embedded in UML models (OCL) • Tools for model-based debugging and testing • [AICA05] Andrea Baruzzo, Executable Models: Formal Specifications Embedded in Software Models, Congresso annuale AICA, Udine, 5-7 ottobre 2005 Code correctness

  4. Problems to address • Due to the complexity of large software systems, preserving model consistency is an issue • Model-based verification is often achieved by means of dynamic checking of OCL constraints … • …but the generation of suitable code which checks them • slows down performance • can alter the behavior • it does not ensure to reveal a bug • generation of just a significative finite subset of the possible runs is not so feasible too • Static Model-based verification (very difficult) • Static Verification of UML model consistency (a first step) • What is inconsistency all about? • A discrepancy between theentire modeland thecode(difficult) • A discrepancy between the specification and the model views (a first step)

  5. Short-term Goals • Verify the dynamic view of the system against the static view and its constraints (“software contracts”) • Identify and refine specifications too strong • Identify new constraints (specifications too weak?) • Build preciseUMLmodels • Class diagrams • Sequence diagrams • Statechart diagrams • (OCL) specifications (the software contract) • Independence from the specification language (OCL, Promela, Alloy,…)

  6. Long-term Goals • Verification • Verify the code of the system against the entire model and its constraints (“software contracts”) • Specification synthesis • From existing code • Tool Integrations • Integration between the static approach (it cannot be complete) e the dynamic approach • Manipulation of the models hierarchy (MDA)

  7. Precise semantics of OCL and UML [Gogolla&Richter01] • Syntax of Object Models • Set of classes (or types) • Set of attributes for each class • Set of associations with role names and multiplicities • Generalization hierarchy over classes M={CLASS, ATTc, OPc, ASSOC, associates, roles, multiplicities, <} • Interpretation of Object Models • System state: objects, links and attribute values constitute the state of a system at a particular moment in time σ(M)= (σCLASS, σATT, σASSOC) • The semantics of an object model is the set of all possible system states σ(M) [Gogolla&Richter01] Martin Gogolla and Mark Richter, OCL: Syntax, Semantics, and Tools, LNCS 2263, Object Modeling with the OCL, 2001

  8. The notion of class correctness • But what happens when this does not hold? • Faulty Program or Inconsistent Specification? • Due to the size of most systems, bugs in assertions are not so unlikely! [Meyer92] Bertrand Meyer, Applying Design by Contract, ACM Computer, Volume 25,  Issue 10, 1992

  9. The method – The process (BEDAV) • Build the UML model of the system • Build the structure view • Build the dynamic (behavioral) view • Enrich the model with the (OCL) specifications • Decompose sequence diagrams in blocks • Annotate each block with formulas to be imposed and to be checked • Verify sequence diagrams against the formulas of each block

  10. The method at work – the model

  11. The method at work – the (OCL) specifications

  12. The method at work - decomposition

  13. The method at work – decomposition

  14. The method at work – validation (equations checked)

  15. {Company.employee −> excludes(Andrea)} … now the diagram becomes consistent!

  16. Work in progress, future works • Work in progress • Tool implementation • Assistant to write OCL constraints (some will be code independent, others not) • Development of the method for Static Model-based verification(with code) • Future works • Support for concurrency • Support for temporal logic (in general, any temporal constraint) • Support for class diagram consistency in itself (i.e. consistency of cardinality constraints in associations)

  17. THANK YOU! 

  18. The method at work – validation (equations imposed)

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