Domain Theory for Modeling OOP: A Summary (Domain Theory for The Construction of NOOP, and The Construction of COOP as a Step Towards Constructing NOOP)

Domain theory is ‘a mathematical theory that serves as a foundation for the semantics of programming languages’ [AJ94]. Domains form the basis of a theory of partial information, which extends the familiar notion of partial function to encompass a whole spectrum of “degrees of definedness”, so as to model incremental higher-order computation (i.e., computing with infinite data values, such as functions defined over an infinite domain like the domain of integers, infinite trees, and such as objects of object-oriented programming). General considerations from recursion theory dictate that partial functions are unavoidable in any discussion of computability. Domain theory provides an appropriately abstract setting in which the notion of a partial function can be lifted and used to give meaning to higher types, recursive types, etc. NOOP is a domain-theoretic model of nominally-typed OOP [Abd12, Abd13, Abd14, CA13, AC14]. NOOP was used to prove the identification of inheritance and subtyping in mainstream nominally-typed OO programming languages and the validity of this identification. In this report we first present the definitions of basic domain theoretic notions and domain constructors used in the construction of NOOP, then we present the construction of a simple structural model of OOP called COOP as a step towards the construction of NOOP. Like the construction of NOOP, the construction of COOP uses earlier presented domain constructors. Objects of OOP are typically infinite data values because they are usually recursivelydefined via their definitions using the special self-referential variables “this” or “self”.