Australian Computer Society
As the eXtensible Markup Language (XML) is about to emerge as a new standard for databases, the problem of providing solid logical grounds for XML query languages arises. For the relational data model first-order logic, i.e. the relational calculus turned out to be an intuitive basic approach to provide these foundations. For XML, however, it is necessary to deal with ordered trees. In this paper, the problem is approached by viewing XML as a data model based on complex objects that are arranged in a class hierarchy.