The process of creating explicit links between terms in distinct controlled vocabularies (e.g., thesauri, subject headings, classification labels) — such as equivalence, broader/narrower, or related-term relations — to enable cross-vocabulary retrieval and interpretation.

Principle

Term‑level mappings specify the semantic relation and directionality between controlled terms so that queries and indexing can be translated or expanded across vocabularies without presuming full ontological equivalence.

Demonstration

Illustrative scenario → Library A uses subject heading 'Automobiles'; Library B uses 'Cars'. Recognition → a mapping Equivalence(Automobiles, Cars) is created with provenance and scope notes. Action → a search for 'Automobiles' is expanded to include 'Cars' in the other catalogue. Consequence → users retrieve relevant records across both catalogues despite different preferred terms.

Misapplication

Assuming a mapped pair denotes exact logical equivalence in every context (ignoring scope notes, qualifiers, or hierarchical differences) causes overbroad retrieval or incorrect subject assignment.

Consequence

Proper mappings improve cross‑catalogue discovery and interoperability; poorly specified mappings create noisy results, missed distinctions, or incorrect automated classifications.

Reversal

When vocabularies have incompatible scopes, update cadences, or proprietary restrictions, automated mapping may be infeasible; in such cases manual mediation, annotations, or limited crosswalks with provenance are required.

Boundary

Clearly within: explicit term‑to‑term assertions (equivalence, broader/narrower) between controlled vocabularies. Boundary case: mapping a vocabulary term to a folksonomy tag. Clearly outside: full ontology alignment involving class/property semantics beyond term relations.

Semantic Tension

Standardization versus local descriptive needs — mappings support unified retrieval at the cost of suppressing local indexing nuances that serve specialized communities.

Synthesis

Vocabulary mapping operationalizes pragmatic access across systems: it is primarily about retrieval interoperability, not about asserting deep semantic identity, and it requires documenting scope and limitations.