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Version: v0.1.6

Resolve a code system to its canonical URI

A coding names its system in whatever form its source used: an OID in HL7 v2 and C-CDA, a mnemonic such as LN in an HL7 v2 coded element, a URI in FHIR. Before you look a code up, test it against a value set or translate it, turn that name into the canonical URI your releases and maps use.

Resolve the name​

import { resolveSystem, isUnknownSystem } from "@cosyte/terminology";

const names = ["2.16.840.1.113883.6.96", "urn:oid:2.16.840.1.113883.6.96", "SCT", "sct", " http://SNOMED.info/sct "];
const urls = names.map((name) => {
  const system = resolveSystem(name);
  return isUnknownSystem(system) ? "unknown" : system.url;
});

new Set(urls); // => new Set(["http://snomed.info/sct"])

resolveSystem accepts a canonical URI (in any letter case), a mnemonic (in any letter case), and an OID, bare or with the urn:oid: prefix. Leading and trailing spaces are trimmed. The result is the system's identity: its url, its oid, a name and its mnemonics. The systems it knows by name are listed on Code-system identities.

Resolve an HL7 v2 table​

HL7 v2 tables are recognized by pattern rather than by a list, from the table's OID or its terminology.hl7.org URI:

import { resolveSystem, isUnknownSystem } from "@cosyte/terminology";

const byOid = resolveSystem("2.16.840.1.113883.12.203");
isUnknownSystem(byOid) ? "unknown" : byOid.url; // => "http://terminology.hl7.org/CodeSystem/v2-0203"

const byUrl = resolveSystem("http://terminology.hl7.org/CodeSystem/v2-0203");
isUnknownSystem(byUrl) ? "unknown" : byUrl.oid; // => "2.16.840.1.113883.12.203"

A table number of one to four digits is accepted. The short form v2-0203 on its own is not recognized: pass the OID or the URI.

Handle a name the engine does not know​

An identifier the engine does not recognize comes back as { unknown: true, input }, never as a guessed URI. The result carries no code field, so branch on isUnknownSystem (the code reference says how this outcome relates to TERM_SYSTEM_UNRECOGNIZED) and decide what your code does with a system it cannot name: reject the record, or keep the original value and flag it.

import { resolveSystem, isUnknownSystem } from "@cosyte/terminology";

const system = resolveSystem("http://example.org/fhir/CodeSystem/house-codes");
isUnknownSystem(system); // => true
isUnknownSystem(system) ? system.input : system.url; // => "http://example.org/fhir/CodeSystem/house-codes"

input echoes what you passed, so treat it like the rest of the record it came from.

Your own local systems will not resolve: the engine knows the systems on the identities page and the HL7 v2 tables, nothing else. If your data uses a local URI, compare it yourself before calling resolveSystem, or keep your own table of local names beside it.

Reference​