Routing XML queries

A vast amount of information currently accessible over the Web, and in corporate networks, is stored in a variety of databases, and is being exported as XML data. However, querying this totality of information in a declarative and timely fashion is problematic because this set of databases is dynamic, and a common schema is difficult to maintain. The present invention provides a solution to the problem of issuing declarative, ad hoc XPath queries against such a dynamic collection of XML databases, and receiving timely answers. There is proposed a decentralized architectures, under the open and the agreement cooperation models between a set of sites, for processing queries and updates to XML data. Each site consists of XML data nodes. (which export their data as XML, and also pose queries) and one XML router node (which manages the query and update interactions between sites). The architectures differ in the degree of knowledge individual router nodes have about data nodes containing specific XML data. There is therefore provided a method for accessing data over a wide area network comprising: providing a decentralized architecture comprising a plurality of data nodes each having a database, a query processor and a path index, and a plurality of router nodes each having a routing state, maintaining a routing state in each of the router nodes, broadcasting routing state updates from each of the databases to the router nodes, routing path queries to each of the databases by accessing the routing state.