An XML resolver should be used to uniquely identify an XML Schema in order to map to a local resource. The DITA specification includes both URN- and URL-based versions of the XML schemas. The URL versions are included as a convenience for use with tools that do not support catalog based resolution and are not normative.
The catalog identifiers use the following patterns.
where:
Note that "oasis" is the owner identifier; this indicates that the artifacts are owned by OASIS. The keyword "dita" is a convention that indicates that the artifact is DITA-related. The pattern "urn:oasis:names:tc:dita" is a convention that indicates that the artifact is DITA-related and defined by the OASIS DITA Technical Committee.