====== Operational Stability ====== [[dido:99_annexes:annex-b-terms-and-definitions:start|Go up to Terms and Definitions]] ===== Discussion ===== Operational Stability is a [[dido:99_annexes:annex-b-terms-and-definitions:q:quality_characteristic|Quality Characteristic]] concerning the degree to which the operational characteristics of a subject remain within permitted variation under specified conditions for a specified period. Operational Stability can apply to: * A [[dido:99_annexes:annex-b-terms-and-definitions:c:candidate_solution|Candidate Solution]] * A [[dido:99_annexes:annex-b-terms-and-definitions:d:distributed_system|Distributed System]] * A [[dido:99_annexes:annex-b-terms-and-definitions:n:node|Node]] * A [[dido:99_annexes:annex-b-terms-and-definitions:n:node_set|Node Set]] * A service * A software component * A hardware component * An [[dido:99_annexes:annex-b-terms-and-definitions:e:execution_facility|Execution Facility]] * An [[dido:99_annexes:annex-b-terms-and-definitions:o:operational_resource|Operational Resource]] * Another subject having observable operational characteristics Operational characteristics can include: * Response time * Throughput * Resource utilization * Availability * Error frequency * Failure frequency * Queue depth * Data-processing rate * State-transition rate * Communication latency * Storage utilization * Energy consumption * Another characteristic established by the [[dido:99_annexes:annex-b-terms-and-definitions:a:acceptance_criteria|Acceptance Criteria]] Operational Stability can identify: * The evaluated subject * The selected operational characteristics * The specified conditions * The evaluation period * The applicable workload * The applicable [[dido:99_annexes:annex-b-terms-and-definitions:t:test_environment|Test Environment]] * The applicable [[dido:99_annexes:annex-b-terms-and-definitions:c:configuration|Configuration]] * The applicable reference values * The permitted variation * The measurement intervals * The measurement methods * The measurement units * The required measurement precision * The treatment of transient behavior * The treatment of warm-up periods * The treatment of planned changes * The treatment of nondeterministic behavior * The applicable DIDO [[dido:99_annexes:annex-b-terms-and-definitions:b:baseline|Baseline]] * The applicable [[dido:99_annexes:annex-b-terms-and-definitions:v:validation_criteria|Validation Criteria]] * The applicable Acceptance Criteria * Its [[dido:99_annexes:annex-b-terms-and-definitions:e:evidence|Evidence]] * Its [[dido:99_annexes:annex-b-terms-and-definitions:p:provenance|Provenance]] * Its [[dido:99_annexes:annex-b-terms-and-definitions:t:traceability|Traceability]] Operational Stability can be evaluated using: * Variation around a reference value * Variation over time * Frequency of excursions outside a permitted range * Duration of excursions outside a permitted range * Trend analysis * Statistical dispersion * Change-point detection * Comparison with a controlling DIDO Baseline * Another method established by the Acceptance Criteria ===== Definition ===== //[[dido:99_annexes:annex-b-terms-and-definitions:q:quality_characteristic|Quality Characteristic]] concerning the degree to which the operational characteristics of a subject remain within permitted variation under specified conditions for a specified period// ===== Source ===== Adapted from: * [[https://www.iso.org/standard/78176.html|ISO/IEC 25010:2023, Systems and software Quality Requirements and Evaluation (SQuaRE) — Product quality model]] * [[dido:99_annexes:annex-b-terms-and-definitions:q:quality_characteristic|Quality Characteristic]] * [[dido:99_annexes:annex-b-terms-and-definitions:r:reliability|Reliability]] * [[dido:99_annexes:annex-b-terms-and-definitions:p:performance_efficiency|Performance Efficiency]] * DIDO Reference Implementation Conceptual Model * DIDO-TE draft Requirements Register * DIDO-TE Broad Agency Announcement source material The DIDO-TE source material identifies Stability as a central evaluation value but does not establish an independently measurable definition. ISO/IEC 25010 does not identify Operational Stability as a separate top-level product-quality characteristic. This definition introduces Operational Stability to provide a measurable interpretation of stability for DIDO-TE comparative evaluation. ===== Note ===== Operational Stability differs from [[dido:99_annexes:annex-b-terms-and-definitions:r:reliability|Reliability]]: * Operational Stability concerns variation in selected operational characteristics * Reliability concerns performance of specified functions under specified conditions for a specified period A subject can remain operational and reliable while exhibiting unacceptable variation in response time or resource utilization. A subject can exhibit stable performance while consistently producing incorrect results. Operational Stability differs from [[dido:99_annexes:annex-b-terms-and-definitions:p:performance_efficiency|Performance Efficiency]]: * Operational Stability concerns variation over time or operating conditions * Performance Efficiency concerns performance relative to resources used Operational Stability does not mean the operational characteristics remain constant. Normal operation can include permitted variation caused by: * Workload changes * Scheduling * Communication delays * Resource allocation * Nondeterministic processing * Maintenance activity * Planned state transitions The applicable Acceptance Criteria establish which variation is permitted. The term **Stability** should not appear alone in a requirement when its intended meaning is Operational Stability. Other meanings of stability can include: * Numerical stability * Configuration stability * Interface stability * Organizational stability * Financial stability Those meanings require separate terms or explicit qualification. ===== Example ===== DIDO-TE evaluates three Candidate Solutions for 24 hours under the same variable workload. The Acceptance Criteria establish permitted ranges for: * Response time * Throughput * Processor utilization * Memory utilization * Queue depth * Communication latency DIDO-TE records each characteristic at defined measurement intervals. One Candidate Solution maintains every characteristic within the permitted variation. Another Candidate Solution completes the same work but exhibits repeated response-time and queue-depth excursions. The comparative evaluation identifies the first Candidate Solution as having greater Operational Stability under the evaluated conditions. ---- © 2026 Dido Solutions, Inc. and Jackrabbit Consulting, Inc.