Arcade a formal extensible model based dependability evaluation framework
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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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Arcade a formal extensible model based dependability evaluation framework

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


Motivation goals

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


Our solution arcade methodology

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


What s an i o imc

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


Sketch of the proposal

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


Arcade current status

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


Example results

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


Arcade tool chain

Arcade: Tool chain

AADL/UML workshop - Belfast


Arcade a summary

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


Extra slides

Extra slides

AADL/UML workshop - Belfast


Arcade example 2

Arcade: Example 2

AADL/UML workshop - Belfast


The state space battle

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


The state space battle1

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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