# Ontology Evolution **Domain:** Ontology Engineering / Knowledge Representation / Change Management **Doc Type:** Canonical Concept Node **Maturity:** Developed ## Definition **Ontology evolution** is the controlled modification of an ontology as its domain, evidence, requirements or conceptual understanding changes. It includes adding and removing concepts, refining definitions, splitting or merging classes, revising relations and evaluating the consequences of those changes. Evolution differs from uncontrolled drift because the change is identified, justified and propagated with attention to consistency and dependency. ## Corpus Context Within [[wiki/Bidirectional Ontology|Bidirectional Ontology]], articles can expose missing distinctions, counterexamples or relationships that the current ontology cannot represent. Those discoveries become proposed changes rather than silent local redefinitions. The weight of review should follow the concept's maturity and reach. Revising an exploratory node may be inexpensive. Revising a foundational node can alter the meaning of many articles and should include an impact review followed, when appropriate, by [[wiki/Corpus Recompilation|Corpus Recompilation]]. ## Change Operations - Add a concept that represents a genuinely distinct object or mechanism. - Refine inclusion and exclusion boundaries. - Split a concept that has collapsed materially different phenomena. - Merge nodes that are aliases without independent explanatory work. - Add, remove or retype relationships. - Deprecate a term while preserving its provenance and former uses. - Revise maturity or authority when evidence changes. ## Key Insight **A living ontology changes, but its changes should remain more legible than the drift they are intended to prevent.** ## Sources / Provenance - Incorporated into the vault's governance model through [[journal/2026-08-15 - Bidirectional Ontology and Semantic Elasticity|2026-08-15 — Bidirectional Ontology and Semantic Elasticity]]. - Ontology evolution is an established knowledge-engineering problem concerning change, consistency, versioning and downstream impact. ## See Also [[wiki/Bidirectional Ontology|Bidirectional Ontology]], [[wiki/Ontology Learning|Ontology Learning]], [[wiki/Semantic Governance|Semantic Governance]], [[wiki/Semantic Elasticity|Semantic Elasticity]], [[wiki/Semantic Drift|Semantic Drift]], [[wiki/Corpus Recompilation|Corpus Recompilation]], [[wiki/Provenance|Provenance]]