Object-oriented Implementation Issues in an Experimental CAD System

This case study of object-oriented program design illustrates two limitations of object-oriented programming languages. Existing object-oriented languages do not have good facilities to support two key program design problems: the definition of composite objects, or data structures that include sets of related subobjects; and the specification and run-time management of temporary data structures required to implement efficient algorithms. Both composite objects and temporary data structures are important to the construction of a wide variety of programs. We use the design and implementation of an interactive computer-aided design system to describe how the limitations of present object-oriented languages complicate the design of composite objects and temporary data structures.