NucLexNuclear Medicine Lexicon and Theranostics Ontology
Stage W0: private living prototype12 of 30 manuscripts drafted, 0 reviewed; 50 lexicon entries in draftWhat each later stage would need to show

Lexicon · Mathematical and computational foundations

Lexicon entryDraftNX-C018

Code system

Fully specified name: Code system (concept)

A system defining codes and their meanings; FHIR CodeSystem represents information about such a system.

Scope note
Distinguish code definitions from selections for a particular use.
Synonyms
None recorded as true synonyms in this context.
Monograph
FHIR terminology resources (draft)
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

A code system is the authority that defines a set of codes and what each one means: SNOMED CT, LOINC, ICD-10-CM, a units system such as UCUM, or a local list maintained by a department. Each code has a meaning fixed by the system's own rules, and the system has a version. In FHIR (Fast Healthcare Interoperability Resources) the CodeSystem resource describes such a system for exchange: its canonical URL, version, content mode (complete, fragment, or not present), properties, and, when the content is included, its concepts with their displays and definitions.

The scope note draws the line that FHIR itself draws. A code system defines codes. A Value set selects some of them for a particular use, such as the codes allowed in one field of one form. Confusing the two leads to a familiar error: treating a departmental pick list as if it were the authority on meaning, or treating the whole of SNOMED CT as if it were the list of permitted values for a field.

For NucLex the distinction is directly relevant. The lexicon is an editorial seed, not a code system; its NX- identifiers are local. If a NucLex vocabulary were ever published as a FHIR CodeSystem it would need a canonical URL, a version policy, and governance, none of which exists in W0. The FHIR R5 CodeSystem page is the authoritative reference.

Sources consulted (1)
  • https://www.hl7.org/fhir/R5/codesystem.html