Web metadata semantics-on the road to well formed topic maps

Topic maps are standardized by ISO 13250 for the purpose of semantic annotation of WWW resources. Recently, the specification has been augmented by a timely XML serialization (by the so called XTM group). With topic maps generic metadata are used to characterize and semantically identify resources. According to certain rules, topic maps can be combined to build global knowledge bases facilitating the search for information within the WWW. Although XTM specifies some natural language style constraints on topic map structures, questions concerning the semantics of topic maps are left open. After introducing topic maps basics, we address problems which may arise. We define a topic map metamodel directly derived from the UML metamodel and show how semantic constraints for topic maps can be formulated using the standard UML object constraint language, i.e., OCL.