Specializing Topic Types in DITA
http://www.ibm.com/developerworks/xml/library/x-dita2/index.html

Priestley, Michael
IBM
2001

Abstract:

The Darwin Information Typing Architecture (DITA) provides a way for documentation authors and architects to create collections of typed topics that can be easily assembled into various delivery contexts. Topic specialization is the process by which authors and architects can define topic types, while maintaining compatibility with existing style sheets, transforms, and processes. The new topic types are defined as an extension, or delta, relative to an existing topic type, thereby reducing the work necessary to define and maintain the new type.