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Saturated semantics for reactive systems
 LOGIC IN COMPUTER SCIENCE
, 2006
"... The semantics of process calculi has traditionally been specified by labelled transition systems (LTS), but with the development of name calculi it turned out that reaction rules (i.e., unlabelled transition rules) are often more natural. This leads to the question of how behavioural equivalences (b ..."
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The semantics of process calculi has traditionally been specified by labelled transition systems (LTS), but with the development of name calculi it turned out that reaction rules (i.e., unlabelled transition rules) are often more natural. This leads to the question of how behavioural equivalences (bisimilarity, trace equivalence, etc.) defined for LTS can be transferred to unlabelled transition systems. Recently, in order to answer this question, several proposals have been made with the aim of automatically deriving an LTS from reaction rules in such a way that the resulting equivalences are congruences. Furthermore these equivalences should agree with the intended semantics, whenever one exists. In this paper we propose saturated semantics, based on a weaker notion of observation and orthogonal to all the previous proposals, and we demonstrate the appropriateness of our semantics by means of two examples: logic programming and a subset of the open πcalculus. Indeed, we prove that our equivalences are congruences and that they coincide with logical equivalence and open bisimilarity respectively, while equivalences studied in previous works are strictly finer.
Bisimulation by unification
 Proc. AMAST 2002, LNCS 2422
, 2002
"... Abstract. We propose a methodology for the analysis of open systems based on process calculi and bisimilarity. Open systems are seen as coordinators (i.e. terms with placeholders), that evolve when suitable components (i.e. closed terms) fill in their placeholders. The distinguishing feature of ou ..."
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Abstract. We propose a methodology for the analysis of open systems based on process calculi and bisimilarity. Open systems are seen as coordinators (i.e. terms with placeholders), that evolve when suitable components (i.e. closed terms) fill in their placeholders. The distinguishing feature of our approach is the definition of a symbolic operational semantics for coordinators that exploits spatial/modal formulae as labels of transitions and avoids the universal closure of coordinators w.r.t. all components. Two kinds of bisimilarities are then defined, called strict and large, which differ in the way formulae are compared. Strict bisimilarity implies large bisimilarity which, in turn, implies the one based on universal closure. Moreover, for process calculi in suitable formats, we show how the symbolic semantics can be defined constructively, using unification. Our approach is illustrated on a toy process calculus with ccslike communication within ambients. 1
A connector algebra for P/T nets interactions
 CONCUR, volume 6901 of LNCS
, 2011
"... Abstract. A quite flourishing research thread in the recent literature on componentbased system is concerned with the algebraic properties of various kinds of connectors for defining wellengineered systems. In a recent paper, an algebra of stateless connectors was presented that consists of five k ..."
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Abstract. A quite flourishing research thread in the recent literature on componentbased system is concerned with the algebraic properties of various kinds of connectors for defining wellengineered systems. In a recent paper, an algebra of stateless connectors was presented that consists of five kinds of basic connectors, plus their duals. The connectors can be composed in series or in parallel and employing a simple 1state buffer they can model the coordination language Reo. Pawel Sobocinski employed essentially the same stateful extension of connector algebra to provide semanticspreserving mutual encoding with some sort of elementary Petri nets with boundaries. In this paper we show how the tile model can be used to extend Sobocinski’s approach to deal with P/T nets, thus paving the way towards more expressive connector models. 1
First Order and Higher Order Tile Models for Open and Mobile Systems
 In Proceedings of TOSCA'00, Workshop Annuale del Progetto TOSCA, 2000. Virtual Proceedings
, 2000
"... h ground and open terms in a uniform way. To this aim, transition labels become pairs, whose components are called triggers (expressing the interaction of a context with its arguments) and effect (representing the behavior offered to the rest of the system, i.e. a possible context). Tiles can be rep ..."
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h ground and open terms in a uniform way. To this aim, transition labels become pairs, whose components are called triggers (expressing the interaction of a context with its arguments) and effect (representing the behavior offered to the rest of the system, i.e. a possible context). Tiles can be represented as rectangles where the horizontal dimension is devoted to the assembling of states and the vertical dimension is dedicated to the evolution of components. Thus, triggers and effects form the left and right sides of tiles, respectively. The vertices of tiles are called interfaces, connecting the input and output observations to the initial (before the step) and final (after the step) configurations. Thanks to the abstract notions of configuration and observation, tiles allow us to develop a theoretical framework parametric in such structures (e.g. graphs or hypergraphs or trees or lterms rather than terms), and able to capture analogies in the structures by means of suitable auxili
Coalgebraic Semantics for Parallel Derivation Strategies in Logic Programming
"... Abstract. Logic programming, a class of programming languages based on firstorder logic, provides simple and efficient tools for goaloriented proofsearch. Logic programming supports recursive computations, and some logic programs resemble the inductive or coinductive definitions written in functi ..."
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Abstract. Logic programming, a class of programming languages based on firstorder logic, provides simple and efficient tools for goaloriented proofsearch. Logic programming supports recursive computations, and some logic programs resemble the inductive or coinductive definitions written in functional programming languages. In this paper, we give a coalgebraic semantics to logic programming. We show that ground logic programs can be modelled by either Pf Pfcoalgebras or Pf Listcoalgebras on Set. We analyse different kinds of derivation strategies and derivation trees (prooftrees, SLDtrees, andor parallel trees) used in logic programming, and show how they can be modelled coalgebraically.
On hierarchical graphs: reconciling bigraphs, gsmonoidal theories and gsgraphs ⋆
"... Abstract. Compositional graph models for global computing systems must account for two relevant dimensions, namely nesting and linking. In Milner’s bigraphs the two dimensions are made explicit and represented as loosely coupled structures: the place graph and the link graph. Here, bigraphs are comp ..."
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Abstract. Compositional graph models for global computing systems must account for two relevant dimensions, namely nesting and linking. In Milner’s bigraphs the two dimensions are made explicit and represented as loosely coupled structures: the place graph and the link graph. Here, bigraphs are compared with an earlier model, gsgraphs, based on gsmonoidal theories and originally conceived for modelling the syntactical structure of agents with αconvertible declarations. We show that gsgraphs are quite convenient also for the new purpose, since the two dimensions can be recovered by introducing two types of nodes. With respect to bigraphs, gsgraphs can be proved essentially equivalent, with minor differences at the interface level. We argue that gsgraphs have a simpler and more standard algebraic structure for representing both states and transitions, and can be equipped with a simple type system (in the style of relational separation logic) to check the wellformedness of bounded gsgraphs. Another advantage concerns a textual form in terms of sets of assignments, which can make implementation easier in rewriting frameworks like Maude. Vice versa, the reactive system approach developed for bigraphs needs yet to be addressed in gsgraphs. 1
Connector Algebras, Petri Nets, and BIP ⋆
"... Abstract. In the area of componentbased software architectures, the term connector has been coined to denote an entity (e.g. the communication network, middleware or infrastructure) that regulate the interaction of independent components. Hence, a rigorous mathematical foundation for connectors is ..."
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Abstract. In the area of componentbased software architectures, the term connector has been coined to denote an entity (e.g. the communication network, middleware or infrastructure) that regulate the interaction of independent components. Hence, a rigorous mathematical foundation for connectors is crucial for the study of coordinated systems. In recent years, many different mathematical frameworks have been proposed to specify, design, analyse, compare, prototype and implement connectors rigorously. In this paper, we overview the main features of three notable frameworks and discuss their similarities, differences, mutual embedding and possible enhancements. First, we show that Sobocinski’s nets with boundaries are as expressive as Sifakis et al.’s BI(P), the BIP component framework without priorities. Second, we provide a basic algebra of connectors for BI(P) by exploiting Montanari et al.’s tile model and a recent correspondence result with nets with boundaries. Finally, we exploit the tile model as a unifying framework to compare BI(P) with other models of connectors and to propose suitable enhancements of BI(P). 1
Relational and Allegorical Semantics for Constraint Logic Programming
, 2012
"... Facultad de Informática ..."