Pr4 UG co Annotation

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Annotation properties (commonly referred to as "annotations") allow arbitrary information to be added to selected portions of an OWL ontology. Although some annotations are specific to a given ontology, a number of annotations are in general use.

Like other properties, annotations are name/value pairs. The name is typically a Uniform Resource Identifier (URI) such as owl:versionInfo or rdfs:label. This allows the annotation's interpretation to be unambiguously specified.

From the model theoretic point of view, these properties are comments. All annotation properties are ignored by the reasoner, and they may not themselves be structured by further axioms. owl:AnnotationProperty assertions can have as objects either individuals or data values, including rdf:XMLLiterals, thus can embed arbitrary XML, including RDF/XML (e.g., Annotea comments), XHTML, or SVG. The built-in annotation properties rdfs:label and rdfs:comment are already extensively used in user interfaces (e.g., tool tips) and in end-user renderings of ontologies.


The value of an annotation is always a text string, but most values are more constrained than this, as:

  • a data literal in a particular format (eg, date, float, integer)
  • a prior version of the ontology
  • a URI referring to a related resource (eg, another ontology)