Results 11  20
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27
Ordered SOS Process Languages for Branching and Eager Bisimulations
 INFORMATION AND COMPUTATION
, 2002
"... We present a general and uniform method for defining structural operational semantics (SOS) of process operators by traditional Plotkinstyle transition rules equipped with orderings. This new feature allows one to control the order of application of rules when deriving transitions of process terms. ..."
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We present a general and uniform method for defining structural operational semantics (SOS) of process operators by traditional Plotkinstyle transition rules equipped with orderings. This new feature allows one to control the order of application of rules when deriving transitions of process terms. Our method is powerful enough to deal with rules with negative premises and copying. We show that rules with orderings, called ordered SOS rules, have the same expressive power as GSOS rules. We identify several classes of process languages with operators defined by rules with and without orderings in the setting with silent actions and divergence. We prove that branching bisimulation and eager bisimulation relations are preserved by all operators in process languages in the relevant classes.
A Polyadic Modal µCalculus
, 1994
"... The propositional µcalculus of Kozen extends modal logic with fixed points to achieve a powerful logic for expressing temporal properties of systems modelled by labelled transition systems. We further extend Kozen's logic with polyadic modalities to allow for expressing also quite naturally be ..."
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The propositional µcalculus of Kozen extends modal logic with fixed points to achieve a powerful logic for expressing temporal properties of systems modelled by labelled transition systems. We further extend Kozen's logic with polyadic modalities to allow for expressing also quite naturally behavioural relations like bisimulation equivalence and simulation preorders. We show that the problem of model checking is still efficiently decidable, giving rise to efficient worstcase algorithms for verifying the infinity of behavioural relations expressible in this polyadic modal µcalculus. Some of these algorithms compete in efficiency with carefully handcrafted algorithms found in the literature. In spite of this result, the validity problem turns out to be highly undecidable. This is in contrast to the propositional µcalculus where it is decidable in deterministic exponential time. It follows as a corollary, that  also in contrast to the propositional µcalculus  the polyadic modal...
NATURAL QUANTUM OPERATIONAL SEMANTICS WITH PREDICATES
, 2008
"... A general definition of a quantum predicate and quantum labelled transition systems for finite quantum computation systems is presented. The notion of a quantum predicate as a positive operatorvalued measure is developed. The main results of this paper are a theorem about the existence of generalis ..."
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A general definition of a quantum predicate and quantum labelled transition systems for finite quantum computation systems is presented. The notion of a quantum predicate as a positive operatorvalued measure is developed. The main results of this paper are a theorem about the existence of generalised predicates for quantum programs defined as completely positive maps and a theorem about the existence of a GSOS format for quantum labelled transition systems. The first theorem is a slight generalisation of D’Hondt and Panagaden’s theorem about the quantum weakest precondition in terms of discrete support positive operatorvalued measures.
Weak Parametric Failure Equivalences and Their Congruence Formats
"... Weak equivalences are important behavioral equivalences in the course of specifying and analyzing the reactive systems using process algebraic languages. In this paper, we propose a series of weak equivalences named weak parametric failure equivalences, which take two previouslyknown behavioral equ ..."
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Weak equivalences are important behavioral equivalences in the course of specifying and analyzing the reactive systems using process algebraic languages. In this paper, we propose a series of weak equivalences named weak parametric failure equivalences, which take two previouslyknown behavioral equivalences, i.e., the weak failure equivalence and the weak impossible future equivalence, as their special cases. More importantly, based on the idea of the structural operational semantics, a series of rule formats are further presented to congruence format for their corresponding weak parametric failure equivalences, i.e., a specific equivalence is further congruent in any languages satisfying its corresponding congruence format. This series of rule formats reflect the gradual changes in the weak parametric failure equivalences. We conclude that, when the weak parametric failure equivalences become coarser, their corresponding rule formats turn tighter.
Research Retrospective
"... The group was exciting in the 1970’s, when we were groping for direction and divided by different orientations. I guess it was in this atmosphere that combined purpose with uncertainty where I found my own voice. The common goal was a transformational program development methodology that would impro ..."
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The group was exciting in the 1970’s, when we were groping for direction and divided by different orientations. I guess it was in this atmosphere that combined purpose with uncertainty where I found my own voice. The common goal was a transformational program development methodology that would improve productivity of designing and maintaining correct software. The emphasis was on algorithmic software. We differed as to how to achieve this goal, and my approach was out on a limb. Based on a few transformations, the most exciting of which was Jay Earley’s iterator inversion combined with high level strength reduction, and also on an overly optimistic faith in the power of science to shed light on this subject, I believed that algorithms and algorithmic software could be designed scientifically from abstract problem specifications by application of a small number of rules, whose selection could be simplified (even automated in some cases) if it could be guided by complexity. Most all others (including the SETL crowd at Courant) disagreed, and accepted the notion that algorithm design was ‘inspired’, and that the most significant steps in a derivation were unexplainable ‘Eureka ’ steps. I knew that my goals were ambitious and with little supporting evidence. In fact the
An NSF proposal
, 2005
"... The objectives of this research are to improve software productivity, reliability, and performance of complex systems. The approach combines program transformations, sometimes in reflective ways, to turn very high level perspicuous specifications into efficient implementations. These transformatio ..."
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The objectives of this research are to improve software productivity, reliability, and performance of complex systems. The approach combines program transformations, sometimes in reflective ways, to turn very high level perspicuous specifications into efficient implementations. These transformations will be implemented in a metatransformational system, which itself will be transformed from an executable specification into efficient code. Experiments will be conducted to assess the research objectives in scaled up applications targetted to systems that perform complex program analysis and translation. The transformations to be used include dominated convergence (for implementing fixed points efficiently), finite differencing (for replacing costly repeated calculations by less expensive incremental counterparts), data structure selection (for simulating associative access on a RAM in real time), and partial evaluation (for eliminating interpretive overhead and simplification). Correctness of these transformations, of userdefined transformations, and of the transformational system itself will be addressed in part. Both the partial evaluator and components of the
Towards a Theory of Glue
"... We propose and study the notions of behaviour type and composition operator making a first step towards the definition of a formal framework for studying behaviour composition in a setting sufficiently general to provide insight into how the componentbased systems should be modelled and compared. W ..."
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We propose and study the notions of behaviour type and composition operator making a first step towards the definition of a formal framework for studying behaviour composition in a setting sufficiently general to provide insight into how the componentbased systems should be modelled and compared. We illustrate the proposed notions on classical examples (Traces, Labelled Transition Systems and Coalgebras). Finally, the definition of memoryless glue operators, takes us one step closer to a formal understanding of the separation of concerns principle stipulating that computational aspects of a system should be localised within its atomic components, whereas coordination layer responsible for managing concurrency should be realised by memoryless glue operators. 1
An Efficient Simulation Algorithm on Kripke Structures
 ACTA INFORMATICA
"... A number of algorithms for computing the simulation preorder (and equivalence) on Kripke structures are available. Let Σ denote the state space, → the transition relation and Psim the partition of Σ induced by simulation equivalence. While some algorithms are designed to reach the best space boun ..."
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A number of algorithms for computing the simulation preorder (and equivalence) on Kripke structures are available. Let Σ denote the state space, → the transition relation and Psim the partition of Σ induced by simulation equivalence. While some algorithms are designed to reach the best space bounds, whose dominating additive term is Psim  2, other algorithms are devised to attain the best time complexity O(Psim→). We present a novel simulation algorithm which is both space and time efficient: it runs in O(Psim  2 log Psim  + Σ  log Σ) space and O(Psim→  log Σ) time. Our simulation algorithm thus reaches the best space bounds while closely approaching the best time complexity.