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13
Algorithmic nominal game semantics
, 2010
"... Abstract. We employ automata over infinite alphabets to capture the semantics of a finitary fragment of ML with groundtype references. Our approach is founded on game semantics, which allows us to translate programs into automata in such a way that contextual equivalence is characterized by a finit ..."
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Cited by 15 (6 self)
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Abstract. We employ automata over infinite alphabets to capture the semantics of a finitary fragment of ML with groundtype references. Our approach is founded on game semantics, which allows us to translate programs into automata in such a way that contextual equivalence is characterized by a finitary notion of bisimilarity. As a corollary, we derive a decidability result for a class of firstorder programs, including open ones that contain unspecified firstorder procedures. 1
COMPLEXITY HIERARCHIES BEYOND ELEMENTARY
, 2013
"... We introduce a hierarchy of fastgrowing complexity classes and show its suitability for completeness statements of many non elementary problems. This hierarchy allows the classification of many decision problems with a nonelementary complexity, which occur naturally in logic, combinatorics, formal ..."
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Cited by 11 (4 self)
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We introduce a hierarchy of fastgrowing complexity classes and show its suitability for completeness statements of many non elementary problems. This hierarchy allows the classification of many decision problems with a nonelementary complexity, which occur naturally in logic, combinatorics, formal languages, verification, etc., with complexities ranging from simple towers of exponentials to Ackermannian and beyond.
Model Checking Languages of Data Words
"... We consider the modelchecking problem for data multipushdown automata (DMPA). DMPA generate data words, i.e, strings enriched with values from an infinite domain. The latter can be used to represent an unbounded number of process identifiers so that DMPA are suitable to model concurrent programs ..."
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Cited by 9 (4 self)
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We consider the modelchecking problem for data multipushdown automata (DMPA). DMPA generate data words, i.e, strings enriched with values from an infinite domain. The latter can be used to represent an unbounded number of process identifiers so that DMPA are suitable to model concurrent programs with dynamic process creation. To specify properties of data words, we use monadic secondorder (MSO) logic, which comes with a predicate to test two word positions for data equality. While satisfiability for MSO logic is undecidable (even for weaker fragments such as firstorder logic), our main result states that one can decide if all words generated by a DMPA satisfy a given formula from the full MSO logic.
A Fresh Approach to Learning Register Automata
, 2013
"... This paper provides an Angluinstyle learning algorithm for a class of register automata supporting the notion of fresh data values. More specifically, we introduce session automata which are well suited for modeling protocols in which sessions using fresh values are of major interest, like in secu ..."
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Cited by 5 (1 self)
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This paper provides an Angluinstyle learning algorithm for a class of register automata supporting the notion of fresh data values. More specifically, we introduce session automata which are well suited for modeling protocols in which sessions using fresh values are of major interest, like in security protocols or adhoc networks. We show that session automata (i) have an expressiveness partly extending, partly reducing that of register automata, (ii) admit a symbolic regular representation, and (iii) have a decidable equivalence and modelchecking problem (unlike register automata). Using these results, we establish a learning algorithm to infer session automata through membership and equivalence queries. Finally, we strengthen the robustness of our automaton by its characterization in monadic secondorder logic.
An automaton over data words that captures EMSO logic
 CONCUR’11, volume 6901 of LNCS
"... Abstract. We develop a general framework for the specification and implementation of systems whose executions are words, or partial orders, over an infinite alphabet. As a model of an implementation, we introduce class register automata, a oneway automata model over words with multiple data values. ..."
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Abstract. We develop a general framework for the specification and implementation of systems whose executions are words, or partial orders, over an infinite alphabet. As a model of an implementation, we introduce class register automata, a oneway automata model over words with multiple data values. Our model combines register automata and class memory automata. It has natural interpretations. In particular, it captures communicating automata with an unbounded number of processes, whose semantics can be described as a set of (dynamic) message sequence charts. On the specification side, we provide a local existential monadic secondorder logic that does not impose any restriction on the number of variables. We study the realizability problem and show that every formula from that logic can be effectively, and in elementary time, translated into an equivalent class register automaton. 1
Full Abstraction for Nominal Scott Domains
, 2013
"... We develop a domain theory within nominal sets and present programming language constructs and results that can be gained from this approach. The development is based on the concept of orbitfinite subset, that is, a subset of a nominal sets that is both finitely supported and contained in finitely m ..."
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Cited by 2 (1 self)
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We develop a domain theory within nominal sets and present programming language constructs and results that can be gained from this approach. The development is based on the concept of orbitfinite subset, that is, a subset of a nominal sets that is both finitely supported and contained in finitely many orbits. This concept appears prominently in the recent research programme of Bojańczyk et al. on automata over infinite languages, and our results establish a connection between their work and a characterisation of topological compactness discovered, in a quite different setting, by Winskel and Turner as part of a nominal domain theory for concurrency. We use this connection to derive a notion of Scott domain within nominal sets. The functionals for existential quantification over names and ‘definite description ’ over names turn out to be compact in the sense appropriate for nominal Scott domains. Adding them, together with parallelor, to a programming language for recursively defined higherorder functions with name abstraction and locally scoped names, we prove a full abstraction result for nominal Scott domains analogous to Plotkin’s classic result about PCF and conventional Scott domains: two program phrases have the same observable operational behaviour in all contexts if and only if they denote equal elements of the nominal Scott domain model. This is the first full abstraction result we know of for higherorder functions with local names that uses a domain theory based on ordinary extensional functions, rather than using the more intensional approach of game semantics.
Denotational Semantics with Nominal Scott Domains
, 2014
"... When defining computations over syntax as data, one often runs into tedious issues concerning αequivalence and semantically correct manipulations of binding constructs. Here we study a semantic framework in which these issues can be dealt with automatically by the programming language. We take the ..."
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When defining computations over syntax as data, one often runs into tedious issues concerning αequivalence and semantically correct manipulations of binding constructs. Here we study a semantic framework in which these issues can be dealt with automatically by the programming language. We take the userfriendly ‘nominal’ approach in which bound objects are named. In particular, we develop a version of Scott domains within nominal sets and define two programming languages whose denotational semantics are based on those domains. The first language, λνPCF, is an extension of Plotkin’s PCF with names that can be swapped, tested for equality and locally scoped; although simple, it already exposes most of the semantic subtleties of our approach. The second language, PNA, extends the first with name abstraction and concretion so that it can be used for metaprogramming over syntax with binders. For both languages, we prove a full abstraction result for nominal Scott domains analogous to Plotkin’s classic result about PCF and conventional Scott domains: two program phrases have the same observable operational behaviour in all contexts if and only if they denote equal elements of the nominal Scott domain model. This is the first full abstraction result we know of for languages combining higherorder functions with some form of locally scoped names which uses a domain theory based on ordinary extensional functions, rather than using the more intensional approach of game semantics.
On Nominal Regular Languages with Binders? Extended version
"... Abstract. We investigate regular languages on infinite alphabets where words may contain binders on names. To this end, classical regular expressions and automata are extended with binders. We prove the equivalence between finite automata on binders and regular expressions with binders and investiga ..."
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Abstract. We investigate regular languages on infinite alphabets where words may contain binders on names. To this end, classical regular expressions and automata are extended with binders. We prove the equivalence between finite automata on binders and regular expressions with binders and investigate closure properties and complementation of regular languages with binders. 1
Nominal Regular Expressions for Languages over Infinite Alphabets Extended Abstract
"... Abstract. We propose regular expressions to abstractly model and study properties of resourceaware computations. Inspired by nominal techniques – as those popular in process calculi – we extend classical regular expressions with names (to model computational resources) and suitable operators (for ..."
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Abstract. We propose regular expressions to abstractly model and study properties of resourceaware computations. Inspired by nominal techniques – as those popular in process calculi – we extend classical regular expressions with names (to model computational resources) and suitable operators (for allocation, deallocation, scoping of, and freshness conditions on resources). We discuss classes of such nominal regular expressions, show how such expressions have natural interpretations in terms of languages over infinite alphabets, and give Kleene theorems to characterise their formal languages in terms of nominal automata. 1