Lexicon · Mathematical and computational foundations
Description logic
Fully specified name: Description logic (concept)
A family of formal languages for representing concepts and relationships and reasoning about them.
- Scope note
- Inferences depend on the logic and axioms supplied.
- Synonyms
- None recorded as true synonyms in this context.
- Monograph
- Description logics (planned; brief only)
- External mappings
- None recorded. In W0 no mapping to SNOMED CT® or any external authority is asserted for this entry. A future mapping record will carry source system, identifier, version, relation type, evidence, author, confidence where meaningful, and review state.
- Formal status
- Editorial entry only. It is not part of any released ontology and a prose edit here changes no formal definition.
Draft. This entry is an unreviewed draft. Its sources have not been checked by a named person and no domain reviewer has approved it. Treat every claim as provisional.
Notes
Description logics (DLs) are decidable fragments of first-order logic designed for defining classes (concepts), properties (roles), and individuals, and for computing consequences such as whether one class is subsumed by another or whether a set of definitions is consistent. Each member of the family trades expressive power against the cost of reasoning. A logic that allows only conjunction and existential restriction can be reasoned over quickly even for very large terminologies; a logic that adds negation, number restrictions, and inverse roles can say more but may make reasoning far slower.
The practical relevance for nuclear medicine is that SNOMED CT is defined in a small description logic (the EL family), which is why a reasoner can compute its hierarchy from stated definitions rather than from hand-placed parents. The Web Ontology Language, OWL, provides profiles corresponding to different description logics. The scope note is the point a reader should keep: a DL reasoner derives only what follows from the axioms it was given, under the semantics of the logic chosen. A surprising inference is more often a sign of a wrong axiom than of a discovery, and the monograph works a small example showing an inference, a non-inference, and the assumptions that separate them.