public:99_annexes:annex-b-terms-and-definitions:o:operational_stability

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public:99_annexes:annex-b-terms-and-definitions:o:operational_stability [2026/09/12 17:42] – removed - external edit (Unknown date) 127.0.0.1public:99_annexes:annex-b-terms-and-definitions:o:operational_stability [2026/09/12 17:43] (current) – ↷ Links adapted because of a move operation nick_dido
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 +====== Operational Stability ======
  
 +[[public:99_annexes:annex-b-terms-and-definitions:start|Go up to Terms and Definitions]]
 +
 +===== Discussion =====
 +
 +Operational Stability is a [[public: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 [[public:99_annexes:annex-b-terms-and-definitions:c:candidate_solution|Candidate Solution]]
 +  * A [[public:99_annexes:annex-b-terms-and-definitions:d:distributed_system|Distributed System]]
 +  * A [[public:99_annexes:annex-b-terms-and-definitions:n:node|Node]]
 +  * A [[public:99_annexes:annex-b-terms-and-definitions:n:node_set|Node Set]]
 +  * A service
 +  * A software component
 +  * A hardware component
 +  * An [[public:99_annexes:annex-b-terms-and-definitions:e:execution_facility|Execution Facility]]
 +  * An [[public: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 [[public: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 [[public:99_annexes:annex-b-terms-and-definitions:t:test_environment|Test Environment]]
 +  * The applicable [[public: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 [[public:99_annexes:annex-b-terms-and-definitions:b:baseline|Baseline]]
 +  * The applicable [[public:99_annexes:annex-b-terms-and-definitions:v:validation_criteria|Validation Criteria]]
 +  * The applicable Acceptance Criteria
 +  * Its [[public:99_annexes:annex-b-terms-and-definitions:e:evidence|Evidence]]
 +  * Its [[public:99_annexes:annex-b-terms-and-definitions:p:provenance|Provenance]]
 +  * Its [[public: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 =====
 +
 +//[[public: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]]
 +  * [[public:99_annexes:annex-b-terms-and-definitions:q:quality_characteristic|Quality Characteristic]]
 +  * [[public:99_annexes:annex-b-terms-and-definitions:r:reliability|Reliability]]
 +  * [[public: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 [[public: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 [[public: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.
 +
 +----
 +
 +<WRAP centeralign>
 +© 2026 Dido Solutions, Inc. and Jackrabbit Consulting, Inc.
 +</WRAP>