Topic maps provide a fairly simple but very powerful metamodel for the representation of knowledge models. In “An Introduction to Topic Maps” (The Architecture Journal, No. 5, 2005), we presented how a combination of topic maps and architecture design patterns allow developers to build reusable components for applications. Now we’ll take a look at some of the current and potential application areas for topic maps. As topic maps are primarily of use when integrated with other systems, we’ll also discuss access to topic map information using a variety of Web services architectures from a traditional RPC-like, client/server interaction to syndication models where either a push model or pull model can be used to interchange updates to a topic map.