METHODS AND INTERFACE FOR BUILDING COMMAND EXPRESSIONS IN A COMPUTER SYSTEM

The system of the present invention comprises a development system having an Expression Builder for assisting a user with creating an expression. With full syntax checking enabled, the user builds an expression in "token" mode. As the user enters each token element, the system attempts to validate the expression and, if the expression is valid, displays the result. If the expression is incomplete or invalid, however, the system displays a message explaining what is needed. The Expression Builder of the present invention employs placeholders or "proxies" for representing elements in an expression which should be replaced before the expression is valid. The expression is dynamically adjusted during user editing as required to maintain expression validity. In this manner, the user is provided with in situ assistance in constructing syntactically-correct expressions.