Research Heaven, West Virginia A Compositional Approach for Validation of Formal Models Bojan Cukic, Dejan Desovski West Virginia University NASA OSMA SAS '04

Research Heaven, West Virginia 2 Problem Informal Problem Description Precise Description Implementation Problem Solving Verification Problem Understanding Validation Formal Domain Significant number of faults in real systems can be traced back to specifications. Proving the correctness of a specification with respect to the requirements is one of the most important and most difficult tasks in the development of High Assurance Systems. Current Methodologies have problems: –Theorem Proving:Too complex for practical use; –Model Checking:State explosion possible –Testing:Not complete. Combining them might be the solution!

Research Heaven, West Virginia 3 Approach Using test coverage measures, decompose the formal specification model. –Abstract the thoroughly tested parts, use model checking on the rest of the specification. Demonstrate that visual interfaces hide the complexity of the specification model. –Develop methodology for creation of visual interfaces. –Use them for representing the coverage metrics too. Extend the SCR toolset –Monitoring specification test coverage. –Automatic decomposition of the specification. –Compositional verification.

Research Heaven, West Virginia 4 Importance/benefits  Verification and validation of formal models suffers from significant practical drawbacks.  Practical and automated assurance of specifications is an open research problem.  Integration of model testing and visual specification interfaces.  Facilitates variable and interaction abstraction.  Abstractions reducing the state-space of the models.  A compositional framework for verification and validation of system specification models.  Exploit the ease of testing, and the completeness of the model checking.  Extending a mature toolset (SCR).

Research Heaven, West Virginia 5 Relevance to NASA Incomplete, inconsistent, unstable system requirements a major mission assurance problem. –Brian O’Connor’s address at NASA IV&V, June 04. Proposed approach to be evaluated on NASA case studies. –Fault Protection Engine (FPE) System at JPL. –Other case studies wanted/needed. Ongoing case studies on formal specification.

Research Heaven, West Virginia 6 Accomplishments Test coverage of SCR specification constructs study completed. –Formally defined coverage criteria applicable to SCR specifications. –SCR’s simulator utilized for automated coverage tracking. –Coverage tracking tool developed, applied to Safety Injection System.

Research Heaven, West Virginia 7 Next Steps  Continue the research on SCR specification test coverage, visualization, abstraction, additional case studies.  Develop a methodology for building visual interfaces of generic SCR specifications.  Investigate visual interfaces suitable for specification verification and validation.  Integrate visualization toolset with the coverage tracking tool.  Research on automated specification abstraction from test coverage metrics.