Over the last two decades there has been an increase in the number of distributed object oriented systems being developed. To assist the development of these systems a number of object oriented modelling techniques have been developed. The Unified Modeling Language was principally designed to combine a number of methodologies into one. As this paper identifies, there are a number of limitations which exist between the mapping of UML designs into IDL. One solution has been to introduce additional keywords into IDLs to provide richer semantics. This paper demonstrates how semantics can be added to interfaces without extending interface definition languages and hence provide software developers with a mechanism to express the dynamic constraints of a distributed object oriented systems.