Scalability

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Discussion

Scalability is a Quality Characteristic concerning the degree to which a subject maintains specified behavior as workload, size, volume, participation, complexity, or allocated resources change within defined limits.

Scalability can apply to:

A marketA deploymentA Candidate SolutionA Distributed SystemA NodeA Qualified NodeA Node SetA serviceA software componentA data storeA communication facilityA governance processAn Execution FacilityAnother subject whose workload, size, participation, complexity, or allocated resources can changeChanges relevant to Scalability can include changes to:

Number of participantsNumber of UsersNumber of NodesNumber of Node SetsNumber of Qualified NodesNumber of governed functionsNumber of work eventsNumber of Evidence ReferencesNumber of Compensation ClaimsNumber of jurisdictionsNumber of Settlement InstructionsNumber of transactionsNumber of requestsNumber of eventsNumber of providersNumber of service instancesData volumeEvidence volumeMessage volumeSettlement-record volumeProcessing rateGeographic distributionDuration of operationGovernance complexityAnother characteristic established by the Acceptance CriteriaAllocated-resource changes can include changes to:

Processor capacityMemoryStorageNetwork capacityNumber of service instancesNumber of Execution FacilitiesNumber of Deployment TargetsNumber of Operational ResourcesAnother allocated ResourceScalability can identify:

The evaluated subjectThe initial workload, size, volume, participation, complexity, or resource allocationThe changed workload, size, volume, participation, complexity, or resource allocationThe applicable scaling directionThe applicable scaling methodThe applicable scaling limitsThe applicable Test EnvironmentThe applicable ConfigurationThe characteristics required to remain within permitted limitsThe applicable measurement methodsThe applicable measurement unitsThe required measurement precisionThe permitted tolerancesThe permitted degradationThe applicable DIDO BaselineThe applicable Validation CriteriaThe applicable Acceptance CriteriaIts EvidenceIts ProvenanceIts TraceabilityTechnical scaling can be:

VerticalHorizontalManualAutomatedUpwardDownwardTemporaryPersistentVertical scaling changes the Resources allocated to an existing instance.

Horizontal scaling changes the number of instances participating in the evaluated operation.

In the Governed Node Service Market, Scalability supports:

Ecosystem growthExpanded jurisdictional participationIncreased provider participationIncreased numbers of Qualified NodesIncreased governed workLarger Evidence volumesIncreased Compensation Claim volumeIncreased Settlement Instruction volumeIncreased settlement-record volumeContinued provider comparisonContinued governance reviewA scalable Governed Node Service Market supports increased size, volume, participation, and complexity while preserving:

Qualification disciplineFunctional obligationsNon-functional obligationsJurisdictional obligationsPolicy obligationsGovernance obligationsEvidence continuityCost attributionProvider comparisonSettlement Traceability

Definition

Quality Characteristic concerning the degree to which a subject maintains specified behavior as workload, size, volume, participation, complexity, or allocated resources change within defined limits

Source

Adapted from:

Financial Systems Archetype, Part 7: Governed Node Service MarketQuality CharacteristicPerformance EfficiencyDIDO Reference Implementation Conceptual ModelDIDO-TE draft Requirements RegisterThe original shared definition described Scalability as the ability of a market or deployment to support increased numbers of participants, Nodes, governed functions, work events, Evidence References, Compensation Claims, jurisdictions, and Settlement Instructions.

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

Note

Scalability differs from capacity:

Capacity identifies a maximum limit under specified conditionsScalability concerns behavior as workload, size, volume, participation, complexity, or allocated resources change within defined limitsScalability differs from Performance Efficiency:

Scalability concerns changes in behavior as evaluation conditions or allocated Resources changePerformance Efficiency concerns performance relative to Resources used under specified conditionsPerformance Efficiency measurements can provide Evidence for a Scalability evaluation.

Scalability differs from Elasticity:

Scalability concerns the degree to which a subject accommodates changes in workload, size, volume, participation, complexity, or allocated ResourcesElasticity concerns adaptation to changing conditions by activating, deactivating, adding, removing, or substituting Resources or Qualified NodesElasticity can be a mechanism for achieving Scalability. Scalability does not require automated adaptation unless the applicable Acceptance Criteria establish that requirement.

Scalability differs from growth:

Growth identifies an increase in size, volume, participation, or complexityScalability concerns whether the subject maintains specified behavior while growth or another defined change occursA subject is not scalable without qualification. A Scalability evaluation must identify:

The characteristic that changesThe evaluated rangeThe required behaviorThe permitted degradationThe applicable measurement conditionsThe applicable comparison methodA subject can scale successfully in one dimension and unsuccessfully in another.

For example:

A Candidate Solution can scale with transaction volume but not with the number of geographically distributed NodesA market can scale with the number of providers but not with the number of jurisdictionsA governance process can scale with work-event volume but not with the number of required reviewsA deployment can scale with processor capacity but not with storage volumeScalability does not mean every measured characteristic remains constant. The Acceptance Criteria establish the permitted variation and degradation as the evaluated conditions change.

Example

A Governed Node Service Market expands from one FX Demo jurisdiction to several jurisdictions.

The number of:

ParticipantsQualified NodesGoverned functionsWork eventsEvidence ReferencesCompensation ClaimsSettlement Instructionsincreases during the evaluation period.

The applicable Acceptance Criteria establish the required behavior, processing limits, response times, Evidence-continuity obligations, provider-comparison obligations, governance-review obligations, and Settlement Traceability requirements.

The market exhibits Scalability when it supports the increased size, volume, participation, and complexity while continuing to satisfy those obligations.

In a separate DIDO-TE evaluation, three Candidate Solutions process increasing transaction workloads under controlled resource allocations. DIDO-TE records performance, Resource Consumption, failures, and permitted degradation at each workload level.

The resulting Test Results support a comparative evaluation of Candidate Solution Scalability.

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