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Causality in Membrane Systems
"... Summary. P systems are a biologically inspired model introduced by Gheorghe Păun with the aim of representing the structure and the functioning of the cell. P systems are usually equipped with the maximal parallelism semantics; however, since their introduction, some alternative semantics have been ..."
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Summary. P systems are a biologically inspired model introduced by Gheorghe Păun with the aim of representing the structure and the functioning of the cell. P systems are usually equipped with the maximal parallelism semantics; however, since their introduction, some alternative semantics have been proposed and investigated. We propose a semantics that describes the causal dependencies occurring between the reactions of a P system. We investigate the basic properties that are satisfied by such a semantics. The notion of causality turns out to be quite relevant for biological systems, as it permits to point out which events occurring in a biological pathway are necessary for another event to happen. 1
Bialgebraic methods in structural operational semantics
 ENTCS
, 2007
"... Bialgebraic semantics, invented a decade ago by Turi and Plotkin, is an approach to formal reasoning about wellbehaved structural operational specifications. An extension of algebraic and coalgebraic methods, it abstracts from concrete notions of syntax and system behaviour, thus treating various k ..."
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Bialgebraic semantics, invented a decade ago by Turi and Plotkin, is an approach to formal reasoning about wellbehaved structural operational specifications. An extension of algebraic and coalgebraic methods, it abstracts from concrete notions of syntax and system behaviour, thus treating various kinds of operational descriptions in a uniform fashion. In this talk, the current state of the art in the area of bialgebraic semantics is presented, and its prospects for the future are sketched. In particular, a combination of basic bialgebraic techniques with a categorical approach to modal logic is described, as an abstract approach to proving compositionality by decomposing modal logics over structural operational specifications. Keywords:
Structural Operational Semantics as a Basis for Static Program Analysis
 In ACM Computing Surveys
, 1996
"... interpretation was defined originally in terms of flowcharts or dynamic discrete systems [3]. From the usual flowchart operational semantics, a socalled static (or collecting) semantics is derived automatically by attaching to each program point (flowchart arc) the set of contexts (states) that f ..."
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interpretation was defined originally in terms of flowcharts or dynamic discrete systems [3]. From the usual flowchart operational semantics, a socalled static (or collecting) semantics is derived automatically by attaching to each program point (flowchart arc) the set of contexts (states) that flow to that point during execution. The collecting semantics summarizes "what really happens at runtime," and the goal of an abstract semantics is to compute properties for the program points that describe the concrete context sets. The abstract semantics does so by executing the flowchart with abstract values that represent context properties. The above formulation is simple and effective, but flowcharts suffer major weaknesses which preclude their use as a general framework for static program analysis: they are too lowlevel and they do not enjoy the compositionality property. A subsequent advance was the formulation of abstract interpretation in a compositional manner via denotational s...
Approximation Semantics and Expressive Predicate Assignment for ObjectOriented Programming (Extended Abstract)
"... Abstract. We consider a semantics for a classbased objectoriented calculus based upon approximation; since in the context of LC such a semantics enjoys a strong correspondence with intersection type assignment systems, we also define such a system for our calculus and show that it is sound and com ..."
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Abstract. We consider a semantics for a classbased objectoriented calculus based upon approximation; since in the context of LC such a semantics enjoys a strong correspondence with intersection type assignment systems, we also define such a system for our calculus and show that it is sound and complete. We establish the link with between type (we use the terminology predicate here) assignment and the approximation semantics by showing an approximation result, which leads to a sufficient condition for headnormalisation and termination. We show the expressivity of our predicate system by defining an encoding of Combinatory Logic (and so also LC) into our calculus. We show that this encoding preserves predicateability and also that our system characterises the normalising and strongly normalising terms for this encoding, demonstrating that the great analytic capabilities of these predicates can be applied to OO. 1
The gamut of dynamic logics
 Handbook of the History of Logic
, 2006
"... Dynamic logic, broadly conceived, is the logic that analyses change by decomposing actions into their basic building blocks and by describing the results of performing actions in given states of the world. The actions studied by dynamic logic can be of various kinds: actions on the memory state of a ..."
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Dynamic logic, broadly conceived, is the logic that analyses change by decomposing actions into their basic building blocks and by describing the results of performing actions in given states of the world. The actions studied by dynamic logic can be of various kinds: actions on the memory state of a computer, actions of a moving robot in a closed world, interactions between cognitive agents performing given communication protocols, actions that change the common ground between speaker and hearer in a conversation, actions that change the contextually available referents in a conversation, and so on. In each of these application areas, dynamic logics can be used to model the states involved and the transitions that occur between them. Dynamic logic is a tool for both state description and action description. Formulae describe states, while actions or programs express state change. The levels of state descriptions and transition characterisations are connected by suitable operations that allow reasoning about pre and postconditions of particular changes.
Verifying distributed systems: the operational approach
, 2009
"... This work develops an integrated approach to the verification of behaviourally rich programs, founded directly on operational semantics. The power of the approach is demonstrated with a stateoftheart verification of a core piece of distributed infrastructure, involving networking, a filesystem, an ..."
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This work develops an integrated approach to the verification of behaviourally rich programs, founded directly on operational semantics. The power of the approach is demonstrated with a stateoftheart verification of a core piece of distributed infrastructure, involving networking, a filesystem, and concurrent OCaml code. The formalization is in higherorder logic and proof support is provided by the HOL4 theorem prover. Difficult verification problems demand a wide range of techniques. Here these include ground and symbolic evaluation, local reasoning, separation, invariants, Hoarestyle assertional reasoning, rely/guarantee, inductive reasoning about protocol correctness, multiple refinement, and linearizability. While each of these techniques is useful in isolation, they are even more so in combination. The first contribution of this paper is to present the operational approach and describe how existing techniques, including all those mentioned above, may be cleanly and precisely integrated in this setting. The second contribution is to show how to combine verifications of individual library functions with arbitrary and unknown user code in a compositional manner, focusing on the problems of private state and encapsulation. The third contribution is the example verification itself. The infrastructure must behave correctly under arbitrary patterns of host and network failure, whilst for performance reasons the code also includes data races on shared state. Both features make the verification particularly challenging.
Modelling Interaction in Agent Systems
 IN 14TH INTERNATIONAL JOINT CONFERENCE IN ARTIFICIAL INTELLIGENCE (IJCAI95
, 1995
"... We present a study of the interaction properties of multiagent systems where agents communicate by means of speech act based primitives. We identify a set of basic interaction mechanisms: agent identity, asynchronous message passing, implicit receive primitive, which are closed to those of the actor ..."
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We present a study of the interaction properties of multiagent systems where agents communicate by means of speech act based primitives. We identify a set of basic interaction mechanisms: agent identity, asynchronous message passing, implicit receive primitive, which are closed to those of the actor model. Then, we define an actor algebra over actor terms as a basic formalism for multiagent systems. Finally, we show how it is possible to translate a speech act based language (a subset of KQML) into the given algebra. This allows to prove the equivalence of multiagent systems in terms of the equivalence of the corresponding actor terms. multiagent systems
Automated synthesis of domainspecific model interpreters
, 2010
"... I dedicate this work to my childhood friend Dave McGregor, who taught me to write my first computer program and opened my eyes to the amazing world of computers. ii Acknowledgments I could never have completed the long, arduous road to the Ph.D. without the help of many people. I have had numerous w ..."
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I dedicate this work to my childhood friend Dave McGregor, who taught me to write my first computer program and opened my eyes to the amazing world of computers. ii Acknowledgments I could never have completed the long, arduous road to the Ph.D. without the help of many people. I have had numerous wonderful teachers over the years. Among these, a few stand out as truly exceptional mentors. In particular, I would like to thank my Ph.D. advisor, Neno Medvidovic. Neno exemplifies every characteristic a graduate student could ask for in an advisor: he is a brilliant scientist, a skilled educator, and a tireless advocate for his students. I would also like to thank the other members of my dissertation committee, Barry Boehm and Sandeep Gupta, for their very constructive critiques of my work. This disseration is undoubtedly stronger because of their input. My undergraduate advisors, Doug Schmidt and Andy Gokhale, were instrumental in my intellectual development. They taught me the fundamental skills of a computer
iRho: an imperative rewriting calculus
, 2008
"... We propose an imperative version of the Rewriting Calculus, a calculus based on pattern matching, pattern abstraction and side effects, which we call iRho. We formulate both a static and bigstep callbyvalue operational semantics of iRho. The operational semantics is deterministic, and immediately ..."
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We propose an imperative version of the Rewriting Calculus, a calculus based on pattern matching, pattern abstraction and side effects, which we call iRho. We formulate both a static and bigstep callbyvalue operational semantics of iRho. The operational semantics is deterministic, and immediately suggests how an interpreter for the calculus may be built. The static semantics is given using a firstorder type system based on a form of product types, which can be assigned to termlike structures (that is, records). The calculus is à la Church, that is, pattern abstractions are decorated with the types of the free variables of the pattern. iRho is a good candidate for the core of a patternmatching imperative language, where a (monomorphic) typed store can be safely manipulated and where fixed points are built into the language itself. Properties such as determinism of the interpreter and subjectreduction have been completely checked using a machineassisted approach with the Coq proof assistant. Progress and decidability of type checking are proved using pen and paper.
A Formal Executable Semantics of Verilog
"... This paper describes a formal executable semantics for the Verilog hardware description language. The goal of our formalization is to provide a concise and mathematically rigorous reference augmenting the prose of the official language standard, and ultimately to aid developers of Verilogbased tools ..."
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This paper describes a formal executable semantics for the Verilog hardware description language. The goal of our formalization is to provide a concise and mathematically rigorous reference augmenting the prose of the official language standard, and ultimately to aid developers of Verilogbased tools; e.g., simulators, test generators, and verification tools. Our semantics applies equally well to both synthesizeable and behavioral designs and is given in a familiar, operationalstyle within a logic providing important additional benefits above and beyond static formalization. In particular, it is executable and searchable so that one can ask questions about how a, possibly nondeterministic, Verilog program can legally behave under the formalization. The formalization should not be seen as the final word on Verilog, but rather as a starting point and basis for community discussions on the Verilog semantics.