Topic maps provide a standard data model for describing complex, interconnected information. ISO/IEC 13250:2000 [ISO] and XTM 1.0 [XTMS] each provide a standard serialization of that data model using SGML and XML syntax. We believe that having addressed the problem of interchange, it is time for the topic map community to consider the development of a standard interface for programming. Developing a standard programming model has the benefits of flattening the learning curve for developers and protecting the investment that businesses make in bespoke topic map application development.

The first wave of topic map applications have been the ‘engines’ - software applications which are, in general, capable of parsing one or both of the standard serialization syntaxes and then exposing the parsed data via an Application Programming Interface (API) which may, or may not, directly reflect the conceptual model of topic maps. However, every implementation of a topic map engine has a different API reflecting the different approaches taken by the developers to representing the topic map data model. While the development of a one-size-fits-all API is probably an unachievable goal, we feel it is necessary for an API developed which is sufficiently fully-featured to meet the majority of topic map application development requirements and to provide a solid foundation for the development of more advanced APIs and topic map applications such as TMQL.

One of the primary factors in the rapid adoption of XML was the early development of a pair of standardized APIs for access to and manipulation of XML data, namely SAX and the DOM. Such standardized APIs have many benefits for developers including a reduced learning curve and the ability to move code from one parser implementation to another. It is our belief that in order to bring topic maps fully into the mainstream, a standardized API for access to and manipulation of topic map data structures is also required. This paper explores some possible forms of APIs for topic maps in an attempt to develop such a standard API which meets the requirements of maximum simplicity; maximum practicality and minimal size. We explore possible means of representation including the extension of the Document Object Model; an abstract graph-based representation and an object-oriented interface based on the XTM Conceptual Model.