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Arcade: A formal, extensible, model-based dependability evaluation framework

Arcade: A formal, extensible, model-based dependability evaluation framework. Hichem Boudali 1 , Pepijn Crouzen 1,2 , Boudewijn R. Haverkort 1 , Matthias Kuntz 1 , Mari ë lle Stoelinga 1. 1 CS, Twente University, The Netherlands 2 CS, Saarland University, Germany. Motivation/Goals.

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Arcade: A formal, extensible, model-based dependability evaluation framework

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  1. Arcade:A formal, extensible, model-based dependability evaluation framework Hichem Boudali1, Pepijn Crouzen1,2, Boudewijn R. Haverkort1, Matthias Kuntz1, Mariëlle Stoelinga1 1CS, Twente University, The Netherlands 2CS, Saarland University, Germany AADL/UML workshop - Belfast

  2. Motivation/Goals • Approaches to dependability evaluation: • Low level (CTMC, SPN, SPA) • Dependability specific (fault trees) • Architecture-based (AADL, UML) • None is perfect, in terms of: • Modeling effort • Hierarchy & modularity • Expressiveness • (formal) Clear semantics • Effective solution techniques Our objective: To devise a formalism that scores high on all these aspects AADL/UML workshop - Belfast

  3. Our solution: Arcade methodology • Architectural approach (system design) • Expressive and extensible • Modular modeling • Formal semantics (based on I/O-IMC) • Efficient state-space generation (compositional-aggregation technique) AADL/UML workshop - Belfast

  4. What’s an I/O-IMC? • Combination of I/O automata and CTMC • Discrete state space • Markovian transitions • Interactive transitions • Action signature • ? - Input actions • ! - Output actions • ; - Internal actions • Behavior of the system results from the composition of its elements. • Well-defined composition operator & bisimulation equivalence (state minimization) λ failed! AADL/UML workshop - Belfast

  5. Sketch of the proposal Control System Process 1 Process 2 Dependability Annotation (User) Bus Processor 1 Processor 2 Result compositional-aggregation Dependability analysis Other analyses Std. solver AADL/UML workshop - Belfast

  6. Arcade: Current status • Use I/O-IMCs as the underlying formal semantics • At an architectural level, we have identified/defined: • (1) Basic (physical/logical) components (BC) • (2) Repair units (RU) • (3) Spare management units (SMU) • All kinds of behaviors/interactions/dependencies, e.g.: • Operational/failure modes • Repair and spare management policies • Functional dependencies • Textual syntax (ultimately graphical and integrate to an ADL) • To each component/unit corresponds a pre-defined basic I/O-IMC • Use I/O-IMCs’ machinery to carry out state-space generation (compositional-aggregation technique) and analysis AADL/UML workshop - Belfast

  7. Example & Results # of states: 98,056 # of transitions: 411,688 Unavailability (50 hours): 6.52100 ∙10-10 Unreliability (50 hours): 52.92420 ∙ 10-10 AADL/UML workshop - Belfast

  8. Arcade: Tool chain AADL/UML workshop - Belfast

  9. Arcade: A summary Architectural Dependability Evaluation with Arcade. Dependable Systems & Networks (DSN 2008), Anchorage, Alaska, USA. • Low modeling effort: • High level & Graphical • Standard features (BC, RU, SMU) • Tight to an ADL (alternative to AADL error annex) • Expressive/Extensible • Standard features, but also (well-structured) user-defined features • Formal semantics (I/O-IMCs) • Compositional & efficient SS generation • Hierarchical modeling AADL/UML workshop - Belfast

  10. Extra slides AADL/UML workshop - Belfast

  11. Arcade: Example 2 AADL/UML workshop - Belfast

  12. The State-Space Battle • Defined and used the I/O-IMC formalism to describe the semantics of each DFT element. • I/O-IMCs: CTMC + I/O transitions. • Semantics of the entire DFT arises naturally as the composition of its elements’ semantics. • Used the compositional-aggregation approach to combat the state-space explosion problem. • Lifted the restrictions  extended DFT formalism. AADL/UML workshop - Belfast

  13. The State-Space Battle Translation Composition + Hiding compositional-aggregation Repeat Aggregation (minimization) Result: System failure probability Aggregatedsystem CTMC CORAL AADL/UML workshop - Belfast

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