1. A method of operating a digital computing system to perform desired data processing operations, said computing system including a programmable processor, a main memory for storing active programs and data, a mass storage memory for storing inactive programs and data, and a display device for visually displaying images in response to processing operations, the method comprising, in combination, the steps of: storing in the mass storage memory a plurality of application programs, each of the application programs being executable independently of each other by said processor, and any given one of the application programs including means for performing one or more generic operations specified by standard requests on corresponding typed data objects stored in the mass storage memory each of said corresponding typed data objects having an associated type classification which indicates an internal structure and interpretation of the data contained in said corresponding typed data objects defined by said given application program, storing in said mass storage memory a database containing entries which, given a specified operation and a specified object type classification, designate a particular one of said application programs that includes means for performing said specified operation on typed data objects having said specified type classification, and storing in said mass storage memory a set of application integration service programs which comprise, in combination, a multitasking application manager program for running selected ones of said application programs concurrently as peer processes in response to program invocation requests from a user or from an already running application program, and a library of common subroutines selectively and individually callable by running application programs, said library including one or more invocation subroutines callable from a first running application program which performs operations on a first data object, said invocation subroutines including means for receiving a request from said first running application program to perform a designated operation on a second data object having a designated object classification, said invocation subroutines further including means responsive to said request for obtaining from said database the identity of a selected second application program including means for performing said designated operation on objects having said designated type classification, and said invocation subroutine further including means for transmitting an invocation request to run said second application program and for transmitting to said second application program a request to perform said designated operation on said second data object.