Abstract: A "navigation protocol" is implemented via a computer program to provide communication and invocation capability among object-oriented application programs and precompiled library routines, collectively referred to as `programs`. Each application program is "registered" with the operating environment during its installation; registration entails updating a registration-table data structure with information about 1) a program identifier; 2) an object-type identifier identifying a class of objects; and 3) an action identifier, e.g., a menu entry, identifying an action which the program can perform on objects of the class specified by the object-type identifier. A user can manipulate an object by selecting the object and requesting that a list of all actions performable on the object be displayed, then selecting one of the displayed possible actions.