Integrity conditions are statements that help determine whether or not given data (for example, a vocabulary) are consistent with respect to the SKOS data model. The purpose of SKOS integrity conditions is to encourage the construction of well-formed and consistent data and to promote interoperability between data represented in SKOS.

  1. kos:ConceptScheme is disjoint with skos:Concept This means  that SKOS concept schemes, or groups of SKOS concepts, must not be on the same hierarchical level as SKOS concepts and vice versa.
  2. skos:prefLabel, skos:altLabel and skos:hiddenLabel are pairwise disjoint properties This means that no SKOS concept may be a member of more than one preferred label, alternate label, and hidden label.
  3. A resource has no more than one value of skos:prefLabel per language tag This means that all SKOS concepts may have only one preferred label for each language tag. For example, the concept summer_squash has the preferred label of “Summer Squash” in English and of “Cucurbita pepo” in Latin, and there may not be any other preferred labels in English or Latin.
  4. skos:related is disjoint with the property skos:broaderTransitive This means that no two SKOS concepts may be connected by both related and broader transitive relationships.
  5. skos:Collection is disjoint with each of skos:Concept and skos:ConceptScheme This means that SKOS collections, or labeled or ordered groups of SKOS concepts, must not be on the same hierarchical level as SKOS concepts and vice versa.
  6. skos:exactMatch is disjoint with each of the properties skos:broadMatch and skos:relatedMatchThis means that no two SKOS concepts may be related by more than one of exact match, broader match, and related match.

For more information about SKOS see https://www.w3.org/TR/skos-reference/