2. The method of claim 1 , wherein one or more custom query operators are implemented in the dynamically built query expression.
1. In a computer networking environment that includes one or more back-end servers providing services and including a plurality of computing systems each having a processor and a memory, with one or more computer systems requesting services from at least one of the back end servers when connected to the networking environment, a computer-implemented method for retrieving and providing features provided by one or more services offered by one or more of the back end servers, the method comprising acts of: executing a dynamic system model for communicating with one or more back-end servers in a network, the dynamic system model comprising metadata structures that define service features for one or more services provided by one or more of the back-end servers and, for each of the one or more of the back-end servers, define a back-end specific syntax understood by the each back-end server, the back-end specific syntax used to invoke and use the services provided by the each back-end server; connecting the dynamic system model to one or more of the back-end servers in the network at runtime, and dynamically updating the metadata structures at runtime to reflect current service features for one or more services offered by one or more of the back-end servers; receiving at a query expression module user input that is to be translated into a proper query syntax and included as part of a query expression used for retrieving service features for one or more services provided by one or more of the back-end servers; connecting the query expression module to the dynamic system model and dynamically building the query expression based on both the user input and information received from the dynamic system model as to available features provided by one or more of the services of one or more of the back-end servers as indicated at runtime by the dynamic system model; executing the dynamically built query expression by sending it to the dynamic system model where the dynamically built query is translated into the back-end specific syntax to run a query on at least one of the one or more of the back-end servers using the back-end specific syntax to retrieve, invoke, and provide the features of the service which are the subject of the query based on the user input and access data stored on the at least one of the one or more of the back-end servers; and the dynamic system model returning the results of the query to the user.