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PSICALCULI: A FRAMEWORK FOR MOBILE PROCESSES WITH NOMINAL DATA AND LOGIC
"... Abstract. The framework of psicalculi extends the picalculus with nominal datatypes for data structures and for logical assertions and conditions. These can be transmitted between processes and their names can be statically scoped as in the standard picalculus. Psicalculi can capture the same ph ..."
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Abstract. The framework of psicalculi extends the picalculus with nominal datatypes for data structures and for logical assertions and conditions. These can be transmitted between processes and their names can be statically scoped as in the standard picalculus. Psicalculi can capture the same phenomena as other proposed extensions of the picalculus such as the applied picalculus, the spicalculus, the fusion calculus, the concurrent constraint picalculus, and calculi with polyadic communication channels or pattern matching. Psicalculi can be even more general, for example by allowing structured channels, higherorder formalisms such as the lambda calculus for data structures, and predicate logic for assertions. We provide ample comparisons to related calculi and discuss a few significant applications. Our labelled operational semantics and definition of bisimulation is straightforward, without a structural congruence. We establish minimal requirements on the nominal data and logic in order to prove general algebraic properties of psicalculi, all of which have been checked in the interactive theorem prover Isabelle. Expressiveness of psicalculi significantly exceeds that of other formalisms, while the purity of the semantics is on par with the original picalculus. 1.
PsiCalculi in Isabelle
 In Proc of the 22nd Conference on Theorem Proving in Higher Order Logics (TPHOLs), volume 5674 of LNCS
"... Abstract. Psicalculi are extensions of the picalculus, accommodating arbitrary nominal datatypes to represent not only data but also communication channels, assertions and conditions, giving it an expressive power beyond the applied picalculus and the concurrent constraint picalculus. We have for ..."
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Abstract. Psicalculi are extensions of the picalculus, accommodating arbitrary nominal datatypes to represent not only data but also communication channels, assertions and conditions, giving it an expressive power beyond the applied picalculus and the concurrent constraint picalculus. We have formalised psicalculi in the interactive theorem prover Isabelle using its nominal datatype package. One distinctive feature is that the framework needs to treat binding sequences, as opposed to single binders, in an efficient way. While different methods for formalising single binder calculi have been proposed over the last decades, representations for such binding sequences are not very well explored. The main effort in the formalisation is to keep the machine checked proofs as close to their penandpaper counterparts as possible. We discuss two approaches to reasoning about binding sequences along with their strengths and weaknesses. We also cover custom induction rules to remove the bulk of manual alphaconversions. 1
Deriving Labels and Bisimilarity for Concurrent Constraint Programming
, 2010
"... Abstract. Concurrent constraint programming (ccp) is a wellestablished model for concurrency that builds upon operational and algebraic notions from process calculi and firstorder logic. Bisimilarity is one of the central reasoning techniques in concurrency. The standard definition of bisimilarity ..."
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Abstract. Concurrent constraint programming (ccp) is a wellestablished model for concurrency that builds upon operational and algebraic notions from process calculi and firstorder logic. Bisimilarity is one of the central reasoning techniques in concurrency. The standard definition of bisimilarity, however, is not completely satisfactory for ccp since it yields an equivalence that is too fine grained. By building upon recent foundational investigations, we introduce a labelled w.r.t. the typical observational equivalence in ccp. This way we provide ccp with a new proof technique for ccp coherent with existing ones.
Applied pi calculus
 Formal Models and Techniques for Analyzing Security Protocols, chapter 6. IOS
, 2011
"... Abstract. The applied pi calculus is a language for modelling security protocols. It is an extension of the pi calculus, a language for studying concurrency and process interaction. This chapter presents the applied pi calculus in a tutorial style. It describes reachability, correspondence, and obs ..."
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Abstract. The applied pi calculus is a language for modelling security protocols. It is an extension of the pi calculus, a language for studying concurrency and process interaction. This chapter presents the applied pi calculus in a tutorial style. It describes reachability, correspondence, and observational equivalence properties, with examples showing how to model secrecy, authentication, and privacy aspects of protocols.
Weak Equivalences in Psicalculi
"... Psicalculi extend the picalculus with nominal datatypes to represent data, communication channels, and logics for facts and conditions. This general framework admits highly expressive formalisms such as concurrent higherorder constraints and advanced cryptographic primitives. We here establish th ..."
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Cited by 10 (5 self)
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Psicalculi extend the picalculus with nominal datatypes to represent data, communication channels, and logics for facts and conditions. This general framework admits highly expressive formalisms such as concurrent higherorder constraints and advanced cryptographic primitives. We here establish the theory of weak bisimulation, where the τ actions are unobservable. In comparison to other calculi the presence of assertions poses a significant challenge in the definition of weak bisimulation, and although there appears to be a spectrum of possibilities we show that only a few are reasonable. We demonstrate that the complications mainly stem from psicalculi where the associated logic does not satisfy weakening. We prove that weak bisimulation equivalence has the expected algebraic properties and that the corresponding observation congruence is preserved by all operators. These proofs have been machine checked in Isabelle. The notion of weak barb is defined as the output label of a communication action, and weak barbed equivalence is bisimilarity for τ actions and preservation of barbs in all static contexts. We prove that weak barbed equivalence coincides with weak bisimulation equivalence. 1
Broadcast Psicalculi with an Application to Wireless Protocols
"... Psicalculi is a parametric framework for extensions of the picalculus, with arbitrary data structures and logical assertions for facts about data. In this paper we add primitives for broadcast communication in order to model wireless protocols. The additions preserve the purity of the psicalcul ..."
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Psicalculi is a parametric framework for extensions of the picalculus, with arbitrary data structures and logical assertions for facts about data. In this paper we add primitives for broadcast communication in order to model wireless protocols. The additions preserve the purity of the psicalculi semantics, and we formally prove the standard congruence and structural properties of bisimilarity. We demonstrate the expressive power of broadcast psicalculi by modelling the wireless adhoc routing protocol LUNAR and verifying a basic reachability property.
Namepassing calculi: from fusions to preorders and types (Appendix)
"... A. Reductionclosed barbed congruence (Section II) ..."
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Spatial and Epistemic Modalities in ConstraintBased Process Calculi
"... Abstract. We introduce spatial and epistemic process calculi for reasoning about spatial information and knowledge distributed among the agents of a system. We introduce domaintheoretical structures to represent spatial and epistemic information. We provide operational and denotational techniques f ..."
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Abstract. We introduce spatial and epistemic process calculi for reasoning about spatial information and knowledge distributed among the agents of a system. We introduce domaintheoretical structures to represent spatial and epistemic information. We provide operational and denotational techniques for reasoning about the potentially infinite behaviour of spatial and epistemic processes. We also give compact representations of infinite objects that can be used by processes to simulate announcements of common knowledge and global information. Introduction. Distributed systems have changed substantially in the recent past with the advent of phenomena like social networks and cloud computing. In the previous incarnation of distributed computing [16] the emphasis was on consistency, fault tolerance, resource management and related topics; these were all characterized by interaction between processes. Research proceeded along two lines: the algorithmic side which
Spatial Information Distribution in Constraintbased
"... Abstract. We introduce spatial and epistemic process calculi for reasoning about spatial information and knowledge distributed among the agents of a system. We introduce domaintheoretical structures to represent spatial and epistemic information. We provide operational and denotational techniques f ..."
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Cited by 2 (2 self)
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Abstract. We introduce spatial and epistemic process calculi for reasoning about spatial information and knowledge distributed among the agents of a system. We introduce domaintheoretical structures to represent spatial and epistemic information. We provide operational and denotational techniques for reasoning about the potentially infinite behaviour of spatial and epistemic processes. We also give compact representations of infinite objects that can be used by processes to simulate announcements of common knowledge and global information. Introduction. Distributed systems have changed substantially in the recent past with the advent of phenomena like social networks and cloud computing. In the previous incarnation of distributed computing [16] the emphasis was on consistency, faulttolerance, resource management and related topics; these were all characterized by interaction between processes. Research proceeded along two lines: the algorithmic side which
Higherorder psicalculi
, 2011
"... Psicalculi is a parametric framework for extensions of the picalculus; in earlier work we have explored their expressiveness and algebraic theory. In this paper we consider higherorder psicalculi through a technically surprisingly simple extension of the framework, and show how an arbitrary psi ..."
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Psicalculi is a parametric framework for extensions of the picalculus; in earlier work we have explored their expressiveness and algebraic theory. In this paper we consider higherorder psicalculi through a technically surprisingly simple extension of the framework, and show how an arbitrary psicalculus can be lifted to its higherorder counterpart in a canonical way. We illustrate this with examples and establish an algebraic theory of higherorder psicalculi. The formal results are obtained by extending our proof repositories in Isabelle/Nominal. 1