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Parameter Dependencies for Component Reliability Specifications
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Parameter Dependencies for Component Reliability Specifications

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Predicting the reliability of a software system at an architectural level during early design stages can help to make systems more dependable and avoid costs for using the implementation. Existing …

Predicting the reliability of a software system at an architectural level during early design stages can help to make systems more dependable and avoid costs for using the implementation. Existing reliability prediction methods for component-based systems use Markov models and assume that the software architect can provide the transition probabilities between individual components. This is however not possible if the components are black boxes, only at the design stage, or not available for testing. We propose a new modelling formalism that includes parameter dependencies into software component reliability speci fications.
It allows the software architect to only model a system-level usage pro le (i.e., parameter values and call frequencies), which a tool then propagates to individual components to determine the transition probabilities
of the Markov model. We demonstrate the applicability of our approach by modelling the reliability of a retail management system and conduct reliability predictions.

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  • 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.

Transcript

  • 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