Frequently Asked Questions about the Darwin Information Typing Architecture (DITA)
http://www.ibm.com/developerworks/xml/library/x-dita3/

Day, Don, Michael Priestley and Gretchen Hargis
IBM
2005

Abstract:

DITA supports the proper construction of specialized DTDs from any higher-level DTD or schema. The base DTD is ditabase DTD, which contains an archetype topic structure and three additional peer topics that are typed specializations from the basic topic: concept, task, and reftopic. The principles of specialization and inheritance resemble the principle of variation in species proposed by Charles Darwin. So the name reminds us of the key extensibility mechanism inherent in the architecture.