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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.
Do As I SaY! Programmatic access control with explicit identities
 In 20th IEEE Computer Security Foundations Symposium
, 2007
"... We address the programmatic realization of the access control model of security in distributed systems. Our aim is to bridge the gap between abstract/declarative policies and their concrete/operational implementations. We present a programming formalism (which extends the asynchronous picalculus wi ..."
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We address the programmatic realization of the access control model of security in distributed systems. Our aim is to bridge the gap between abstract/declarative policies and their concrete/operational implementations. We present a programming formalism (which extends the asynchronous picalculus with explicit principals) and a specification logic (which extends Datalog with primitives from authorization logic). We provide two kinds of static analysis methods to tie implementation to specification. Type checking determines that a program is a sound implementation of policy; i.e., that all granted accesses are safe in the face of arbitrary opponents. Model checking determines a degree of completeness; i.e., that accesses permitted by the policy are actually granted in the implementation. 1.
Freshregister automata
 In Proceedings of the 38th Annual ACM SIGPLANSIGACT Symposium on Principles of Programming Languages (POPL ’11
, 2011
"... What is a basic automatatheoretic model of computation with names and freshname generation? We introduce FreshRegister Automata (FRA), a new class of automata which operate on an infinite alphabet of names and use a finite number of registers to store fresh names, and to compare incoming names wi ..."
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What is a basic automatatheoretic model of computation with names and freshname generation? We introduce FreshRegister Automata (FRA), a new class of automata which operate on an infinite alphabet of names and use a finite number of registers to store fresh names, and to compare incoming names with previously stored ones. These finite machines extend Kaminski and Francez’s FiniteMemory Automata by being able to recognise globally fresh inputs, that is, names fresh in the whole current run. We examine the expressivity of FRA’s both from the aspect of accepted languages and of bisimulation equivalence. We establish primary properties and connections between automata of this kind, and answer key decidability questions. As a demonstrating example, we express the theory of the picalculus in FRA’s and characterise bisimulation equivalence by an appropriate, and decidable in the finitary case, notion in these automata.
Finitely Branching Labelled Transition Systems from Reaction Semantics for Process Calculi
"... We investigate LeiferMilner RPO approach for CCS and π ..."
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We investigate LeiferMilner RPO approach for CCS and π
Network applications of graph bisimulation
 PROCEEDINGS OF THE 4TH INTERNATIONAL CONFERENCE ON GRAPH TRANSFORMATION (ICGT’08), VOLUME 5214 OF LNCS
, 2008
"... Synchronising Graphs is a system of parallel graph transformation designed for modeling process interaction in a network environment. We propose a theory of contextfree synchronising graphs and a novel notion of bisimulation equivalence which is shown to be a congruence with respect to graph compo ..."
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Synchronising Graphs is a system of parallel graph transformation designed for modeling process interaction in a network environment. We propose a theory of contextfree synchronising graphs and a novel notion of bisimulation equivalence which is shown to be a congruence with respect to graph composition and node restriction. We use this notion of equivalence to study some sample network applications, and show that our bisimulation equivalence captures notions like functional equivalence of logical switches, equivalence of channel implementations and level of fault tolerance of a network.
Efficient Bisimilarities from Secondorder Reaction Semantics for πcalculus
, 2010
"... We investigate Leifer and Milner RPO approach for deriving efficient (finitely branching) LTS’s and bisimilarities for πcalculus. To this aim, we work in a category of secondorder term contexts and we apply a general pruning technique, which allows to simplify the set of transitions in the LTS obt ..."
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We investigate Leifer and Milner RPO approach for deriving efficient (finitely branching) LTS’s and bisimilarities for πcalculus. To this aim, we work in a category of secondorder term contexts and we apply a general pruning technique, which allows to simplify the set of transitions in the LTS obtained from the original RPO approach. The resulting LTS and bisimilarity provide an alternative presentation of symbolic LTS and Sangiorgi’s open bisimilarity.
Efficient Bisimilarities from Secondorder Reaction Semantics for picalculus?
"... Abstract. We investigate Leifer and Milner RPO approach for deriving efficient (finitely branching) LTS’s and bisimilarities for picalculus. To this aim, we work in a category of secondorder term contexts and we apply a general pruning technique, which allows to simplify the set of transitions in ..."
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Abstract. We investigate Leifer and Milner RPO approach for deriving efficient (finitely branching) LTS’s and bisimilarities for picalculus. To this aim, we work in a category of secondorder term contexts and we apply a general pruning technique, which allows to simplify the set of transitions in the LTS obtained from the original RPO approach. The resulting LTS and bisimilarity provide an alternative presentation of symbolic LTS and Sangiorgi’s open bisimilarity.
Towards Nominal Formal Languages (long version)
"... Abstract. We introduce formal languages over infinite alphabets where words may contain binders. We define the notions of nominal language, nominal monoid, and nominal regular expressions. Moreover, we extend historydependent automata (HDautomata) by adding stack, and study the recognisability of ..."
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Abstract. We introduce formal languages over infinite alphabets where words may contain binders. We define the notions of nominal language, nominal monoid, and nominal regular expressions. Moreover, we extend historydependent automata (HDautomata) by adding stack, and study the recognisability of nominal languages. 1