Object-oriented Programming - Formal Semantics

Formal Semantics

There have been several attempts at formalizing the concepts used in object-oriented programming. The following concepts and constructs have been used as interpretations of OOP concepts:

• coalgebraic data types
• abstract data types (which have existential types) allow the definition of modules but these do not support dynamic dispatch
• recursive types
• encapsulated state
• Inheritance
• records are basis for understanding objects if function literals can be stored in fields (like in functional programming languages), but the actual calculi need be considerably more complex to incorporate essential features of OOP. Several extensions of System F_<: that deal with mutable objects have been studied; these allow both subtype polymorphism and parametric polymorphism (generics)

Attempts to find a consensus definition or theory behind objects have not proven very successful (however, see Abadi & Cardelli, A Theory of Objects for formal definitions of many OOP concepts and constructs), and often diverge widely. For example, some definitions focus on mental activities, and some on program structuring. One of the simpler definitions is that OOP is the act of using "map" data structures or arrays that can contain functions and pointers to other maps, all with some syntactic and scoping sugar on top. Inheritance can be performed by cloning the maps (sometimes called "prototyping"). OBJECT:=>> Objects are the run time entities in an object-oriented system. They may represent a person, a place, a bank account, a table of data or any item that the program has to handle.