Searching the Internet using the currently available search engines is not satisfactory. The techniques used there focus on the extraction of relevant information directly from the documents available on the World Wide Web. We introduce a new approach, which aims at describing the content of a Web space, formed by a collection of related documents, instead of looking at the single documents. By identifying concepts and the relationships among them, the content of a Web space is described semantically in a schema for the Web space. The main objective is that, by following this approach, we can start querying the content of a collection of related documents rather than the content of a single document. In this paper, we introduce a model for Web spaces that allows us to describe the concepts at a semantic level, in terms of classes, associations over classes and attributes of classes. At the syntactic level, we use XML to describe information as instantiations of the concepts defined in the Web space schema. Dealing with data on the Web implies dealing with semi-structured data. We discuss how this relates to our model for a Web space and show how to deal with these aspects efficiently when moving towards an implementation.