1. A method of controlling application usage and document access in a plurality of computers the method comprising: evaluating at least one rule pertaining to an occurrence of an event, wherein the at least one rule is among a plurality of rules stored on a first computer, wherein the at least one rule comprises at least one expression used by the evaluating step to decide whether to perform an action, wherein the at least one rule comprises an abstraction whose corresponding definition statement is stored at a second computer, separate from the first computer, and wherein evaluating the at least one rule comprises: retrieving the definition statement stored at the second computer; collecting information required to evaluate the definition statement; evaluating the definition statement using the collected information; and determining a result of evaluating the at least one rule using the at least one expression and the evaluated definition statement; communicating with the plurality of computers as indicated by the at least one rule; and instructing the plurality of computers to perform an action as indicated by the at least one rule comprising: determining a low-level file operation to be executed if the action is allowed; if the evaluating the at least one rule results in a Boolean true, allowing the low-level file operation to execute; and if the evaluating the at least one rule results in a Boolean false, disallowing the low-level file operation from executing.