The Ontopia Topic Map Engine is a topic map development SDK written in Java that provides all the functionality needed for building topic map applications.

The Ontopia Topic Map Engine handles all the difficult aspects of topic map development on behalf of applications. The SDK lets applications load topic maps from XML documents, store topic maps in databases, modify and access topic maps, and generally do all an application may need to do with a topic map. The engine has a core topic map API which all applications use to access topic map data, regardless of where those data are stored. Thus, whether the topic map is in-memory, in a database, or a virtual view is all the same to the application.