MESSAGE CONVERSION AND A NEW-TYPE SYSTEM FOR OO MODEL

In this paper, we propose that the messages should be defined independ ently to the class definitions in an object-oriented program. The comp atibility relation between two message types is also discussed. This k ind of relationship is essential and useful for software reuses. A sof tware designer can declare the compatibility relation between two mess age types if messages are defined independently to the class definitio ns. A message of one type can be converted to another type automatical ly when necessary if a compatibility relation between the two message types is specified. A new type system is proposed based on these new c oncepts in this paper. This type system is more flexible than the trad itional ones while keeping the safety of type checking.