coral: a tool for compositional reliability and availability analysis †
DESCRIPTION
Coral: a tool for Compositional Reliability and Availability analysis †. Hichem Boudali 1 , Pepijn Crouzen 2 , and Mari ë lle Stoelinga 1 . 1 Formal Methods and Tools group CS, University of Twente, NL . 2 Dependable Systems and Software group, CS, Saarland University, Germany. - PowerPoint PPT PresentationTRANSCRIPT
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Coral: a tool for CompositionalReliability and Availability analysis†
Hichem Boudali1, Pepijn Crouzen2, and Mariëlle Stoelinga1.
1Formal Methods and Tools groupCS, University of Twente, NL.
2Dependable Systems and Software group,CS, Saarland University, Germany
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Context & Motivation
Systems do fail Reliability Engineering:
- Analyze system reliability Many formalisms: Petri nets, RBDs, DFTs, AADL, DFTs:
- Graphical, popular formalism - Unreliabilty = P[failure during mission time]
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Dynamic Fault trees Graphical, intuitive formalism Specify system failures in terms
of component failure Tree/DAG
leaves: basic events = component failures
gates: failure propagation CORAL methodology
formal semantics using IOIMCs Compositional modeling +
verification state space reduction techniques
phone
engine
road trip
car
tire 1 tire 2 tire 3 tire 4 spare
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Tool Chain
DFT
SVL bcg_labels
DFTrepository
dft2bcg
SVL
IOIMCmodel
dft2bcg dft_evalIOIMCmodels
CTMC +goal state
bcg_trans
mission time
Unrealiability
C O R A L
= P[failure during mission time]
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What is deep compositionality?
Failure
2/3
S
CBA
Semantics of a DFT arises naturally ascomposition of the semantics of its building blocks
But: This may lead to huge models.
f(G1)
f(NE1) f(NE4)…
f(G1)
Translationeach gate gets IOIMC
Composition
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Prototype tool chainCoral – DFT analysis
dft2bcg:Translation
composer:Composition
composer:minimization
composer:Repeat
CTMC
Result:
unreliability
dft_eval:Analysis
dft_eval:MC generation
User-givenordering
1325 statesinstead of32757 states
Composition order
matters
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Tool Chain
DFT
SVL bcg_labels
DFTrepository
dft2bcg
SVL
IOIMCmodel
dft2bcg dft_evalIOIMCmodels
CTMC +goal state
bcg_trans
compositionscript
mission time
Unrealiability
C O R A L
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Case studiesAnalysismethod
Max number of
states
Max number of transitions
Unreliability
MDCS Monolithic 253 1383 2.00 · 10-9
Compositional 190 723 2.00 · 10-9
HCPS Monolithic 4113 24608 1.35 · 10-3
Compositional 133 465 1.35 · 10-3
CAS Monolithic 8 10 0.657
Compositional 32 116 0.657
FTPP Monolithic 32757 426826 2.55479 · 10-8
Compositional 1325 14153 2.55479 · 10-8
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CORAL: lifting previous drawbacks of DFTs
Lack of formal semantics semantics in terms of IOIMCs Each gate & BE has corresp. IOIMC DFT semantics = composition of gate
semantics Lack of modularity
severe restrictions on reuse of sub-models in larger models
CORAL is much more liberal State space explosion problem
use bisimulation to combate state space explosion
phone
engine
road trip
car
tire 1 tire 2 tire 3 tire 4 spare
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Future work Fully automated tool
Get rid of composition script Order of composition matters heuristics
More aggressive state reduction Weaker equivalence, interface constraints, Phase-type
minimization Further extensions to DFT modeling capabilities
Extension to non-exponential distributions New DFT building blocks
Simulation for DFTs Apply deep compositionality to other engineering
formalisms! E.g. Architectural description languages like AADL
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References H. Boudali, P. Crouzen, M. Stoelinga. “Dynamic Fault
Tree analysis using Input/Output Interactive Markov Chains”, DSN 2007 proceedings.
H. Boudali, P. Crouzen, M. Stoelinga. “A compositional semantics for Dynamic Fault Trees in terms of Interactive Markov Chains”, ATVA 2007.
More info: [email protected] [email protected] [email protected]