<?xml version="1.0" encoding="utf-8"?><!DOCTYPE Zthes SYSTEM "http://zthes.z3950.org/xml/zthes-05.dtd">  <Zthes><term><termId>31309560</termId><termName>ontologies</termName><termType>PT</termType><termNote><![CDATA[ Formal, machine-readable specifications of a conceptual model, in which concepts, properties, relationships, functions, constraints, and axioms are all explicitly defined. Refers to a compilation that is not technically a controlled vocabulary, but that uses one or more controlled vocabularies for a defined domain and expresses the vocabulary in a representative language that has a grammar for using vocabulary terms to express something meaningful. Ontologies generally divide their world into the following areas: individuals, classes, attributes, relations, and events. The grammar of the ontology links these areas together by formal constraints that determine how the vocabulary terms or phrases may be used together. ]]></termNote><termCreatedDate>2026-03-30 20:23:22</termCreatedDate><relation><relationType>UF</relationType><termId>31309561</termId><termName>ontology</termName><termType>ND</termType></relation><relation><relationType>BT</relationType><termId>31359448</termId><termName>reference sources</termName><termType>PT</termType></relation><relation><relationType>BT</relationType><termId>31300179</termId><termName>vocabulary</termName><termType>PT</termType></relation><relation><relationType>RT</relationType><termId>31309558</termId><termName>controlled vocabularies</termName><termType>PT</termType></relation></term>  </Zthes>