Everyday a huge number of new information resources are linked to the web. This way the web is growing very fast, making search tasks more and more difficult with worse results. To solve the problem several initiatives were undertaken and a new area of research and development emerged: the one called Semantic Web.

When we refer to the semantic web we are thinking about a network of concepts. Each concept has a group of related resources and can be related to other concepts; we can then use this concept network to navigate among web resources or simply among information resources. From the undertaken initiatives one became an ISO standard: Topic Maps ISO 13250.

The aim of this paper is to introduce a Topic Map™ Builder, that is a processor that extracts topics and relations from instances of a family of XML documents.

A TM-Builder is strongly dependent on the resources structure. So, to extract a topic map for different collections of information resources (sets of documents with different structures) we have to implement several TM-Builders, one for each collection. This is not very easy! To overcome this inconvenient we have created an XML abstraction layer for TM-Builders that enables us to specify the topic map we want to build from a concrete family of resources, in order to generate automatically the intended extractor.

To describe that process, i.e. the extraction of knowledge from XML documents to produce a TM, we present a language to specify topic maps for a class of XML documents, that we call XSTM (XML Specification for Topic Maps). We also discuss a XSL processor that automatically generates the Extractor from its formal specification
written in XSTM, the XSTM-P.