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According to the OWL 2 Web Ontology Language Document Overview (Second Edition), the primary exchange syntax for OWL 2 is RDF/XML. Therefore, every IOF ontology MUST be serialized in the RDF/XML syntax, using more specific rules explained in the subsequent sections.
Base IRI
According to TBD, the xml:base attribute of an XML element determines an IRI prefix to be prepended to every relative IRI used in any nested XML element. The following provides a fictitious example of how this mechanism works:
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Note that the default namespace declaration on line 2 technically make the elements Ontology (lines 6 and 7) and Class (lines 9 and 11) into the fully qualified IRIs http://www.w3.org/2002/07/owl#Ontology and http://www.w3.org/2002/07/owl#Class, respectively, however, the use of any other non-OWL, unqualified XML element would inadvertently put that element into the OWL namespace, which is a violation of TBD.
In order to ensure that no XML element is inadvertently put into the wrong namespace, every IOF ontology MUST NOT declare a default namespace.
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