Maintainability

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Discussion

Maintainability is a Quality Characteristic concerning the degree to which a subject supports effective and efficient analysis, correction, modification, testing, and controlled change.

Maintainability applies to subjects such as:

A Candidate SolutionA Distributed SystemA systemA serviceA software componentA NodeA Qualified NodeA Node SetA governed function implementationA deploymentA ConfigurationAnother subject requiring controlled changeMaintainability concerns activities such as:

AnalysisDiagnosisDefect correctionPolicy updateConfiguration changeInterface changeDependency updateRefactoringTestingRegression testingControlled releaseVersion controlRollbackRetirement of obsolete versionsMaintainability supports long-term operation, qualification continuity, auditability, evidence continuity, and controlled evolution.

A Maintainability evaluation can identify:

The evaluated subjectThe applicable changeThe reason for the changeThe affected componentsThe affected interfacesThe affected dependenciesThe applicable ConfigurationThe applicable VersionThe effort required to analyse the changeThe effort required to implement the changeThe effort required to test the changeThe time required to complete the changeThe defects introduced by the changeThe applicable regression scopeThe applicable rollback procedureThe applicable DIDO BaselineThe applicable Validation CriteriaThe applicable Acceptance CriteriaIts EvidenceIts ProvenanceIts TraceabilityIn the Governed Node Service Market, Maintainability supports:

Long-term operationQualification continuityDefect correctionPolicy updatesConfiguration reviewVersion controlAuditabilityControlled releaseRollbackRetirement of obsolete implementationsA maintainable Qualified Node continues to satisfy its governed function obligations after an approved fix, update, configuration change, policy change, interface change, or deployment change.

Controlled maintenance preserves:

Qualification obligationsFunctional obligationsNon-functional obligationsEvidence obligationsService-level expectationsInteroperabilityTraceability

Definition

Quality Characteristic concerning the degree to which a subject supports effective and efficient analysis, correction, modification, testing, and controlled change

Source

Adapted from:

Financial Systems Archetype, Part 7: Governed Node Service MarketDIDO Reference Implementation Conceptual ModelDIDO-TE draft Requirements RegisterThe original shared definition described Maintainability as the ability of a governed function implementation to support analysis, correction, update, testing, and controlled change.

This revision generalizes the subject for use throughout the shared DIDO corpus while preserving the original Governed Node Service Market application.

Note

Maintainability supports long-term operation and governance.

A maintainable Node supports:

Version controlDefect correctionConfiguration reviewTest EvidenceControlled releaseRollbackRetirement of obsolete versionsMaintainability differs from Portability:

Portability concerns movement across approved platforms, runtimes, or deployment environmentsMaintainability concerns controlled analysis, correction, modification, testing, and changeMaintainability differs from Reliability:

Reliability concerns the degree to which a subject performs specified functions under specified conditions for a specified periodMaintainability concerns the degree to which the subject supports controlled analysis, correction, modification, testing, and changeMaintainability differs from Recoverability:

Recoverability concerns restoration after an interruption or failureMaintainability concerns controlled changes to the subject and its supporting artifactsA maintainable subject does not necessarily require fewer changes. Maintainability concerns the effectiveness, efficiency, control, and verifiability of the change process.

A Maintainability claim requires identified evaluation conditions. Useful measures include:

Time required to identify a defectTime required to locate affected componentsTime required to implement a correctionTime required to complete regression testingNumber of components affectedNumber of defects introducedPercentage of tests automatedPercentage of changes successfully rolled backCompleteness of change EvidenceCompleteness of Traceability

Example

A policy-evaluation Qualified Node receives an approved policy update.

The provider:

Records the applicable change requestIdentifies affected components and interfacesUpdates the implementationRuns the applicable regression testsRecords the resulting Version and EvidenceVerifies continued satisfaction of the governed function obligationsReleases the updated implementation through the controlled release processRetains the preceding Version for rollback according to the applicable policyThe resulting records support evaluation of the Qualified Node's Maintainability.

In a DIDO-TE evaluation, multiple Candidate Solutions receive the same controlled change request. DIDO-TE compares the analysis effort, implementation effort, testing effort, elapsed time, introduced defects, rollback results, Evidence, and Traceability associated with each Candidate Solution.

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