Active XML: A Data-Centric Perspective on Web Services This talk introduces Active XML (AXML, for short), a declarative framework that harnesses Web services for data integration, and is put to work in a peer-to-peer architecture. An AXML document is an XML document that may contain embedded calls to Web services. An AXML "peer" is a repository of AXML documents. On the one hand, it acts as a client, by invoking the calls to Web services embedded in its documents. On the other hand, a peer acts as a server, by providing Web services that can be declaratively specified as queries over the AXML documents it contains. The AXML approach allows to gracefully combine stored information with data defined in an intensional manner (as service calls). The fact that peers can exchange a mixture of materialized and intensional data (via AXML documents) leads to a very powerful distributed data management paradigm. The AXML approach induces a number of technically challenging problems, both theoretical and practical, which I will describe in the talk. I will also present a prototype that we developed, and mention some interesting applications.