Schema-driven Customization of Web Services

XML is becoming the universal format for data exchange between applications. Recently, the use of XML documents, where some of the data is given explicitly, while other parts are de ned by programs that generate the relevant data, started gaining popularity [7, 8, 3]. We refer to such documents as intensional documents. We call Materialization the process of invoking some of the programs included in an XML document and replacing them by their results. We are particularly interested here in documents where the intensional part is given by embedding calls to Web services inside the documents. Web services [11] are emerging as a standard mean of publishing and accessing data on the Web, by providing a standard XML-based protocol to invoke remote programs over the Web (SOAP), along with a standard language to describe them (WSDL). Consequently, they furnish a uniform framework for describing intensional XML data, and were adopted for instance in [7, 8, 3]. The goal of this demonstration is to advocate for the exchange of such intensional XML documents between applications, and to illustrate the new possibilities and the great exibility they bring to application design. The demonstrated software was developed in the context of Active XML [3, 1, 9, 2], a peer-to-peer system that natively supports intensional documents and the declarative speci cation of Web services using XQuery [12]. We propose a new approach that allows one to control and customize the exchange of intensional documents between Active XML peers, but the same principles can be employed for exchanges between arbitrary Web applications. When exchanged between two applications, intensional documents have a crucial property: since Web services can be called from anywhere on the Web, data