Some general conditions under which the specification of a concurrent system can be expressed as the conjunction of specifications for its component processes are explored. A lattice-theoretic fixed-point theorem about increasing functions is proved, and examples of its application in several areas of computing science are given. Some consequences are drawn for the design of concurrent algorithms, high-level programming languages, and fine-grained concurrent computer architectures. >

Concurrent constraint programming [Sar89 ,SR90] is a simple and powerful model of concurrent computation based on the notions of store-as-constraint and process as information transducer. The store-as-valuation conception of von Neumann computing is replaced by the notion that the store is a constraint (a finite representation of a possibly infinite set of valuations) which provides partial information about the possible values that variables can take. Instead of “reading” and “writing” the values of variables, processes may now ask (check if a constraint is entailed by the store) and tell (augment the store with a new constraint). This is a very general paradigm which subsumes (among others) nondeterminate data-flow and the (concurrent) (constraint) logic programming languages. This paper develops the basic ideas involved in giving a coherent semantic account of these languages. Our first contribution is to give a simple and general formulation of the notion that a constraint system is a system of partial information (a la the information systems of Scott). Parameter passing and hiding is handled by borrowing ideas from the cylindric algebras of Henkin, Monk and Tarski to introduce diagonal elements and “cylindrification” operations (which mimic the projection of information induced by existential quantifiers).

/pdf/the-semantic-foundations-of-concurrent-constraint-3afuxdc5t5.pdf

A theory of conjunction and concurrency

The semantic foundations of concurrent constraint programming

Semantic foundations of concurrent constraint programming

TLA + is a language intended for the high-level specification of reactive, distributed, and in particular asynchronous systems. Combining the linear-time temporal logic TLA and classical set-theory, it provides an expressive specification formalism and supports assertional verification.

On the Logic of TLA

Composing invariants

Tony Hoare’s many contributions to computing science are marked by insight that was grounded in practical programming. Many of his papers have had a profound impact on the evolution of our field; they have moreover provided a source of inspiration to several generations of researchers. We examine the development of his work through a review of the development of some of his most influential pieces of work such as Hoare logic, CSP and Unifying Theories.

/pdf/insight-inspiration-and-collaboration-58xraekci4.pdf

Insight, Inspiration and Collaboration

/pdf/a-theory-of-conjunction-and-concurrency-12zc7oov5z.pdf

A theory of conjunction and concurrency

Citations

The semantic foundations of concurrent constraint programming

Semantic foundations of concurrent constraint programming

On the Logic of TLA

Composing invariants

Insight, Inspiration and Collaboration

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