Abstract: A method and system for allowing clients to retrieve data from data sources that do not necessarily support the same protocols and formats as the clients. The clients issue service requests. A pre-processor responds to the requests by generating XML-structured request objects with unresolved links to the data sources that have information required by the clients. An XML processor resolves the links by issuing requests through one or more gateways. The gateways convert the responses received from the data sources into XML, which the XML processor uses to create XML composite response documents. A post-processor filters the XML response documents, and applies XSL stylesheets to transform the XML composite response documents into client-specific responses that conform to the format required by the clients. The client-specific responses are then sent to the clients.