Semantics Of Concurrent Programming Languages Research Articles

Locally Abstract, Globally Concrete Semantics of Concurrent Programming Languages

Formal, mathematically rigorous programming language semantics are the essential prerequisite for the design of logics and calculi that permit automated reasoning about concurrent programs. We propose a novel modular semantics designed to align smoothly with program logics used in deductive verification and formal specification of concurrent programs. Our semantics separates local evaluation of expressions and statements performed in an abstract, symbolic environment from their composition into global computations, at which point they are concretised. This makes incremental addition of new language concepts possible, without the need to revise the framework. The basis is a generalisation of the notion of a program trace as a sequence of evolving states that we enrich with event descriptors and trailing continuation markers. This allows to postpone scheduling constraints from the level of local evaluation to the global composition stage, where well-formedness predicates over the event structure declaratively characterise a wide range of concurrency models. We also illustrate how a sound program logic and calculus can be defined for this semantics.

Relaxed Operational Semantics of Concurrent Programming Languages

We propose a novel, operational framework to formally describe the semantics of concurrent programs running within the context of a relaxed memory model. Our framework features a "temporary store" where the memory operations issued by the threads are recorded, in program order. A memory model then specifies the conditions under which a pending operation from this sequence is allowed to be globally performed, possibly out of order. The memory model also involves a "write grain," accounting for architectures where a thread may read a write that is not yet globally visible. Our formal model is supported by a software simulator, allowing us to run litmus tests in our semantics.

M-nets: An algebra of high-level Petri nets, with an application to the semantics of concurrent programming languages

This paper describes a high-level Petri net model called M-nets (for modular multilabelled nets). A distinctive feature of this model is that it allows both: unfolding, as do most other high-level net models; and composition – in particular, synchronisation – in a process algebraic style, turning the set of M-nets into an algebraic domain. It turns out that the composition operations of this domain have various algebraic properties. Moreover, the model is such that composition operations are coherent with unfolding, in the sense that the unfolding of a composite high-level net is the composition of the unfoldings of its components. One of the motivations for M-nets is that they be a vehicle for giving semantics of concurrent programming languages. To illustrate their capability for that, the compositional semantics of \(B(PN)^2\)– a simple, expressive concurrent programming language – is given. An associated low-level net semantics is described, and the coherence of these high-level and low-level semantics is proved.

A characterization of distance between 1-bounded compact ultrametric spaces through a universal space

The category of 1-bounded compact ultrametric spaces (KUMs) and non-distance increasing functions has been extensively used in the semantics of concurrent programming languages. In this paper a universal space U for KUMs is introduced, such that each KUM can be isometrically embedded in it. The space U consists of a suitable subset of the space of functions from [0, 1) to N, endowed with a “prefix-based” ultrametric. U allows to characterize the distance between KUMs introduced in Alessi et al. (1995) in terms of the Hausdorff distance between its compact subsets. As applications, it is proved how to derive the existence of limits for Cauchy towers of spaces without using the classical categorical construction and how to find solutions of recursive domain equations inside ℘ nco(U) .

Choice principles in hyperuniverses

It is well known that the validity of Choice Principles is problematic in non-standard Set Theories which do not abide by the Limitation of Size Principle. In this paper we discuss the consistency of various Choice Principles with respect to the Generalized Positive Comprehension Principle (GPC). The Principle GPC allows to take as sets those classes which can be specified by Generalized Positive Formulae, e.g. the universe. In particular we give a complete characterization of which choice principles (e.g. the Selection Principle and the Ordering Principle) hold in Hyperuniverses. Hyperuniverses are structures which arose independently in Non-well-founded Set Theory and in Mathematical Semantics of Concurrent Programming Languages and are hitherto the only existing models of GPC. Hyperuniverses are naturally endowed with a κ-compact uniform κ-topology and are uniformly isomorphic to their exponential space, i.e. the space of their closed subsets endowed with the Exponential Uniformity.

On the Action Semantics of Concurrent Programming Languages

<p>Action semantics is a framework for semantic description of prograrnming languages. In this framework, actions are semantic entities, used to represent the potential behaviour of programs --- also the contributions that parts of programs make to such behaviour. The notation for expressing actions, called action notation, is combinator-based. It is used in much the same way that lambda-notation is used in denotational semantics. However, the essence of action notation is operational, rather than mathematical, and its meaning is formally defined by a structural operational semantics together with a bisimulation equivalence.</p><p>This paper briefly motivates action semantics, and explains the basic concepts. It then illustrates the use of the framework by giving an action semantic description of a small example language. This language includes a simple form of concurrency: tasks that may synchronize by means of rendezvous. The paper also discusses the operational semantics of action notation, focusing on the primitive actions that represent asynchronous message transmission and process initiation.</p>