Accessing up-to-date information in a fast and easy way implies the necessity of information management tools to explore and analyse the huge number of available electronic resources. The Web offers a large amount of valuable information, but its human-oriented representation and its size makes extremely difficult any kind of computer-based processing. In this paper, a combination of distributed AI and information extraction techniques is proposed to tackle this problem. In particular, we have designed a multiagent system that composes ontologies from taxonomies of terms. Moreover, the obtained ontology is used to represent, in a structured way, the currently available web resources. The paper analyses the application of this approach in some examples in the medical domain.