Parameter Dependencies for Component Reliability Specifications
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This document presents a solution for determining transition probabilities for component reliability specifications using Markov models. The proposed approach models components as control flow graphs containing internal actions, branches, external calls, loops, and failure probabilities. Parameter dependencies capture how failure probabilities and branch probabilities may depend on input parameters. The model is transformed into a Markov model to calculate component reliability. The approach is demonstrated on a case study of an inventory service component from a retail management system.
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Parameter Dependencies for Component Reliability Specifications
- 1. Parameter Dependencies for Component Reliability Specifications HeikoKoziolek (ABB Corporate Research)Franz Brosch (FZI Karlsruhe, Germany)
- 2. Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 1 EU Project Q-ImPrESS Quality Impact Prediction for Evolving Service-oriented Software www.q-impress.eu
- 3. Software Reliability Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 2 [Musa1987]
- 4. Architecture-basedReliability Analysis Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 3 Markov Model ComponentArchitecture R = 0.9223 ExpectedReliability Markov Model Solution [Trivedi2001]
- 5. Problem Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 4 Howtodeterminethetransitionprobabilities?
- 6. Literature: Existing Approaches Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 5
- 7. Our Solution Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 6
- 8. Our Solution: Model Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 7 Internal Action BranchProbability Sequence Branch External Call
- 9. Our Solution: Model Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 8 FailureProbability BranchProbability ExternalCall Inputs Parameter Dependency Parameter Dependency Input Parameter Input Parameter
- 10. Our Solution: Model Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 9 Loop NumberofIterations
- 11. Our Solution: Model Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 10
- 12. Our Solution: Transformation Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 11
- 13. Our Solution: Markov Model Solution Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 12 R Q [Trivedi2001]
- 14. Case Study: Retail Management System Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 13
- 15. Case Study: Inventory Service - BookSale Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 14
- 16. Case Study: Modelling Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 15 Parameter Dependency on Loop Count ComponentArchitecture PalladioTool Control Flow Graph for a Component Service
- 17. Case Study: Analysis Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 16 PalladioTool Markov Model Solution
- 18. Case Study: ReliabilityPredictionResults Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 17
- 19. Case Study: ReliabilityPredictionResults Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 18
- 20. Assumptions & Limitations Markov Property FailureProbabilities Determiniation? Stochastically Independent Constant Expressiveness No Hardware Failures NoConcurrency NoRepair Getting Parameter Dependencies Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 19
- 21. Conclusion Parameter DependenciesforComponentReliabilitySpecifications Modellingbycomponentdeveloperandsoftwarearchitect Easy alternationofsystem-levelusageprofile Reusablereliabilityspecifications Heiko Koziolek: Parameter Dependencies for Component Reliability Specifications 20 www.q-impress.eu
Editor's Notes
- Quality in the sense ofperformance, maintainability, reliability in this talk: focus on reliability
- Differentlifecyclestages: design, testingTesting: SRGM, curve-fitting on reportedfailures, extrapolation, morethan 40 modelsknownDesign: Goal: determiningsoftwarereliabilitywhenpluggingtogethercomponents
- About 20 approachesknownwhichfollowthiscycleGoal: Validateuserrequirements, improvearchitecture design, selectfittingcomponentsTheperceivedreliabilitydepends on howthecomponentsareused: iftheunreliablefunctionsarecalledonlyseldomly, theoverallreliabilitymight still behighFailureprobabilitiesmightbedetermined via testing individual componentsbythedevelopersAfter computingtheexpectedreliability- reliabilitycanbecomputedforcertaincomponents- find componentsmostlycontributingtooverallreliability- introduceredundancy
- TransitionprobabiltiesbetweenthecomponentarisefromtheusageprofileofthesystemDepending on someuseractions, thecomponentmightpropagatecallsdirectedtothemitis vital tohaveaccuratetransitionprobabilitiesotherwisethepredictionbecomeinaccuratetheproblemisespeciallypronunced in a systemcomposed out ofblack box compoents, whichonlydescribetheprovidedandrequiredinterfaces. Whichprovidedservicecallswhichrequiredservice? The dependencyisunknown. Itmightbethecasethat a providedservicedoes not userequiredservicesat all. Itmightbethecasethat a providedserviceusesmanyrequiredservices. Thisis not visiblefromtheinterfacedescriptionbythecomponentdevelopers
- Onlyfourrepresentativeapproaches- cheungrequiresthewholesystemtobesetupandmeasured, thisis not desirable- hamletisdifficult- reussnerandcheung do not deal withtheissueandassumetheprobabilitiesasgivenorignorethembecausetheyfocus on a singlecomponent.
- Correct y>5!Useannotationsforloop? Multiple internalactions?Correctfailureprobabilitiesfor P2 and P3
- a retail chain to handle its sales and manage its inventory dataservice-orientedsystemwithcustomerandproviderfocus on theservicebookSale() oftheInventorycomponent- retail solution clients invoke this operation at the end of each salesprocess in order to update the stock information
- If we set a goal of 99.99% for the bookSale() reliability, the gure shows thatthis goal is reached with a stock update failure probability of 10-e6 and at most 98items. If the failure probability rises to 2-e6 the goal is only reached with anumber of items smaller than 50.