Jan Rutten

From failure to success: comparing a denotational and a declarative semantics for Horn clause logic

The main purpose of the paper is to relate different models for Horn Clause Logic: operational, denotational, declarative. We study their relationship by contrasting models based on interleaving, on the one hand, to models based on maximal parallelism, on the other. We make use of complete metric spaces as an important mathematical tool, both in defining and in comparing the various models.

On blocks: locality and asynchronous communication

A general construct for locality in languages based on asynchronous communication is introduced which allows a uniform semantic description of such apparently diverse notions as the introduction of local variables in concurrent imperative languages with shared variables and the hiding of logical variables in concurrent constraint languages.

Semantics models for concurrent logic languages

Abstract In this paper we develop semantic models for a class of concurrent logic languages. We give two operational semantics based on a transition system, a declarative semantics and a denotational semantics. One operational and the declarative semantics model the success set, that is, the set of computed answer substitutions corresponding to all successfully terminating computations. The other operational and the denotational semantics also model deadlock and infinite computations. For the declarative and the denotational semantics we extend standard notions such as unification in order to cope with the synchronization mechanism of the class of languages we study. The basic mathematical structure for the declarative semantics is the complete lattice of sets of finite streams of substitutions. In the denotational semantics, we use a complete metric space of tree-like structures that are labelled with functions that represent the basic unification step. We look at the relations between the different models. We relate first the two operational semantics and next the declarative and denotational semantics with their respective operational counterparts.

Horizons of the Mind. A Tribute to Prakash Panangaden: Essays Dedicated to Prakash Panangaden on the Occasion of His 60th Birthday

This Festschrift volume contains papers presented at a conference, Prakash Fest, held in honor of Prakash Panangaden, in Oxford, UK, in May 2014, to celebrate his 60th birthday. Prakash Panangaden has worked on a large variety of topics including probabilistic and concurrent computation, logics and duality and quantum information and computation. Despite the enormous breadth of his research, he has made significant and deep contributions. For example, he introducedlogic and a real-valued interpretation of the logic to capture equivalence of probabilistic processes quantitatively. The 25 papers included in this volume were carefully reviewed. They cover a large variety of topics in theoretical computer science.