Algorithm Simplification Through Object Orientation

The object oriented (O-O) approach is claimed to have a number of advantages. Some support to these claims appeared during an O-O redesign of a legacy CAD system. A surprisingly simple and efficient solution algorithm was discovered for a change propagation problem. The analysis of the case employs the new concepts of implementation and extension complexity, which indicate the amount of code (software costs) required for the implementation and for later extensions. These two complexities are functions of the problem complexity expressed by the number N of object types employed to model the problem domain. Moving from the old system to the new O-O system reduced the implementation complexity from O N ()2 to O N ( ) , the extension complexity is reduced from O N ( ) to O ()1. The two systems have the same space and time complexities. The CAD system is employed for designing structures composed of parts. The O-O analysis attempts to analyze each part type separately, which proved possible. The corresponding N different object types can therefore be developed independently of each other. The top down analysis employed for the old algorithm did not discover the simple architecture, because it is not geared to look for this kind of solutions. Instead it analyzes the N 2 different change propagation cases. The methodical search for independent modules is an important reason for preferring O-O analysis. Key words: object oriented; software architecture; complexity; implementation complexity; extension complexity 1