Introduction

The purpose of this Guide to the XTM Syntax is to help web developers to implement topic map based systems using a syntax that has been provided to facilitate web-compliant topic map applications.

The XML Topic Maps (XTM) syntax is part of the ISO/IEC 13250 Topic Maps standard.

The syntax is expressed as a Document Type Definition (DTD). Click here for the XTM DTD (raw version). An annotated, hyperlinked, version of the XTM DTD, is provided here. Simple examples of XTM code are available on a separate page.

Note. If you are new to XML and want to know what a Document Type Definition (DTD) is and how to read the XTM DTD, explanations are provided here.

Purpose of XTM

The purpose of an XTM document is to provide a way to interchange, in an XML-based notation, information that describes the semantics of information objects and their interrelations. Topic maps are used as a superimposed, external layer over existing information corpora, to facilitate navigation between predefined topics of interest. Topic maps can be seen as the online equivalent as indexes found in the back of printed books. They can also be used as ways to connect heterogeneous repositories containing databases and documents.

Here is a global overview, mainly a list of the element types and attributes used in the XTM DTD. For more details, see either the XTM DTD or the annotated XTM DTD.

Types of elements

Topic Map Basic Constructs:

• High Level elements: topicMap, mergeMapTopic and topic characteristics:topic, subjectIdentity, baseName, occurrence
• Associations and association characteristics:association, member, roleSpec
• Common characteristics: instanceOf, scope
• Reference elements: topicRef, subjectIndicatorRef, resourceRef
• Terminal elements: baseNameString, resourceData
• Variant name: variant, variantName, parameters

Attributes used in the XTM DTD

The id (unique identifier) and xlink:href (simple link) are used throughout the XTM DTD. The other attributes used declare XML namespaces, the xmlns:xlink namespace, xlink:type (xlink type, always "simple" in XTM), and the xml:base attribute.