Multiple substitutability without affecting the taxonomy

Abstract

Two areas where common object-oriented modeling power lacks the necessary expressiveness are identified. An analysis of the situation shows that there exists a single reason why the real world situations cannot be modeled adequately. What really is missing is a means to express that objects of a certain type are able to behave in a faslfion objects of another type would do. To remedy this situation we introduce a single new concept, define its semantics, give a thorough analysis of its applicability in light of strong typing, and illustrate its symbiosis with inheritance and genericity. The concept is illuminated by means of several examples.