1. A method comprising: controlling usage, at a client system, of an application program, wherein the controlling step limits the application program's operational functionality in accordance to at least one rule stored on the client system, and the at least one rule contains at least one expression used by the controlling step to control application program operation; controlling access, at a server, to documents, wherein the controlling step limits document access operation in accordance to at least one rule stored on the server, and the at least one rule contains at least one expression used by the controlling step to control document access operation;