Objects, interference, and the Yoneda embedding

We present a new semantics for Algol-like languages that combines methods from two prior lines of development: 1. the object-based approach of Reddy, where the meaning of an imperative program is described in terms of sequences of observable actions, and 2. the functor-category approach initiated by Reynolds, where the varying nature of the run-time stack is explained using functors from a category of store shapes to a category of cpos. The semantics gives an account of both the phemomena of local state and irreversibility of state change. As an indication of the accuracy obtained, we present a full abstraction result for closed terms of second-order type in a language containing active expressions, i. e. value-returning commands.

Authors

• Peter W. O'Hearn
• Uday S. Reddy

Keywords

• Denotational semantics
• Interference
• Aliasing