This section briefly describes the GooseWorks Toolkit (GwTk), a free, open source, Apache-licensed implementation of the graph-based data model for topic maps specified in the draft Reference Model (dRM) for topic maps under development at ISO (informally, the Graph). GwTk implements the version of the dRM also known as TMPM4. (See Chapter 4 for a discussion of the dRM.)
 For TMPM4, see Steven R. Newcomb and Michel Biezunski, Topicmaps.net's Processing Model for XTM, accessible at http://www.topicmaps.net and http://www.y12.doe.gov/sgml/sc34/document/0243.htm. For the dRM, see Steven R. Newcomb and Michel Biezunski, A High-Level Description of a Draft Reference Model for ISO 13250 Topic Maps, accessible at ...