1. A data processing system, comprising: storage to store information files and associated metadata, the metadata indicating information about the associated information files, said metadata including typed-attributes usable in processing the information files; a database including a plurality of user records, the user records including respective profile data structures, the respective profile data structures including one or more interest nodes, the interest nodes including respective sets of targets, wherein a target comprises a typed-attribute; logic executable to process the information files and associated metadata in response to a selected interest node to produce a filtered set of information files using said targets in said selected interest node; logic executable to compose and send executable documents via a network interface according to a communication protocol to a user terminal for rendition of a graphical interface at a user terminal, wherein the executable documents comprise data specifying a representation of the filtered set of information files and a representation of user selectable mark-up identifying typed-attributes represented by said metadata associated with the filtered set of information files; and logic to receive messages via a network interface according to a communication protocol indicating selection of particular mark-up in the graphical interface at the user terminal, and executable to modify the selected interest node in response to said messages to add a target corresponding to the typed-attribute identified by the particular mark-up.