1. A method comprising: receiving, at a server via web service communications from a client, client web service messages comprising data marked according to a markup language; wherein receiving the client web service messages comprises: receiving a first client web service message to request a connection to the server; receiving a second client web service message associated with the connection, wherein the second client web service message encapsulates an XQuery expression as data marked according to the markup language, wherein the XQuery expression conforms to an XQuery language; at the server, extracting the XQuery expression from the second client web service message; at the server, executing the XQuery expression against XML data; sending, from the server to the client via web service communications, a server web service message; wherein the server web service message contains a sequence of items; wherein the sequence of items contains at least part of results from execution of the XQuery expression; wherein the method is performed by one or more computing devices.