Topic Maps: inner workings

Topic Maps work on a much higher level than usual SGML/XML applications.

In SGML/XML, a reference syntax is used in a DTD to define classes of documents.

The Topic Map DTD only defines the syntax to be used in Topic Maps, classes of Topic Map documents will have to be defined with this syntax.

XTM 1.0 provides a few standardized meta topics (as published subject identifiers PSI) in core.xtm (http://www.topicmaps.org/xtm/1.0/core.xtm).

Applications will have to define such meta topics for their purposes