Introduction

TMShare was created in order to achieve a number of goals:

• to test the use of topic maps in a highly distributed information sharing environment;

• to explore new ways in which peer-to-peer networks can be used to share information rather than content;

• as a practical application of the TM4J topic map engine .

This paper focuses principally on the first of these goals and in particular on how the exchange of subsets of topic map information between peers can be used as the basis for information sharing in a distributed environment. The author has chosen to call these exchanged subsets topic map fragments. The paper describes the techniques used by both the information provider and the information receiver in an exchange to select the subset to be encoded as a topic map fragment and to incorporate multiple topic map fragments to present a coherent view of the information available from a collection of interacting peers. Topic map fragments are combined with each other and with locally held topic map information using the topic map merge process defined in the XML Topic Maps specification . The principle feature of that process is that when two topics are determined to represent the same subject, all of the information provided by those topics are combined into a single topic in the merged result. Although the context described here is that of a peer-to-peer application, these concepts of selecting and interchanging topic map fragments can be applied to more traditional client-server applications.