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Elie Najm - One of the best experts on this subject based on the ideXlab platform.
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Assembling components with behavioural contracts
Annales Des Télécommunications, 2005Co-Authors: Cyril Carrez, Alessandro Fantechi, Elie NajmAbstract:Component based design is a new paradigm to build distributed systems and applications. The problem of compositional verification of such systems is however still open. We investigate methods and concepts for the provision of “sound” assemblies. We define a behavioural interface type language endowed with a (Decidable) Set of interface compatibilty and subtyping rules. We define an abstract, dynamic, multi-threaded, component model, encompassing both client/server and peer to peer communication patterns. Based on the notion of compliance of components to their interfaces, we define the concepts of “contract” and “contract satisfaction”. This leads to sound assemblies of components, which possess interesting properties, such as “external deadlockfreeness” and “message consumption”.
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Assembling components with behavioural contracts
Annales Des Télécommunications, 2005Co-Authors: Cyril Carrez, Alessandro Fantechi, Elie NajmAbstract:La conception basée composants est une nouvelle méthode de construction d’applications et de systèmes distribués. La vérification compositionnelle de ces systèmes reste cependant un problème ouvert. Nous étudions des méthodes et des concepts pour la construction d’assemblages « sains ». Nous définissons un langage de type d’interfaces comportementales, doté d’un ensemble de règles (décidables) de compatibilité d’interface et de sous-typage. Nous définissons un modèle de composant abstrait, dynamique et multi-tâche, qui englobe les modèles client/serveur et point-à-point. Basé sur la notion de conformité du composant par rapport à son interface, nous définissons les concepts de « contrat » et « respect de contrat ». Cela mène aux assemblages sains de composants qui possèdent des propriétés intéressantes, comme «l’absence d’interblocage externe » et «la consommation des messages». Component based design is a new paradigm to build distributed systems and applications. The problem of compositional verification of such systems is however still open. We investigate methods and concepts for the provision of “sound” assemblies. We define a behavioural interface type language endowed with a (Decidable) Set of interface compatibilty and subtyping rules. We define an abstract, dynamic, multi-threaded, component model, encompassing both client/server and peer to peer communication patterns. Based on the notion of compliance of components to their interfaces, we define the concepts of “contract” and “contract satisfaction”. This leads to sound assemblies of components, which possess interesting properties, such as “external deadlockfreeness” and “message consumption”.
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FORTE - Behavioural Contracts for a Sound Assembly of Components
Formal Techniques for Networked and Distributed Systems - FORTE 2003, 2003Co-Authors: Cyril Carrez, Alessandro Fantechi, Elie NajmAbstract:Component based design is a new methodology for the construction of distributed systems and applications. In this new Setting, a system is built by the assembly of (pre)-existing components. Remains the problem of the compositional verification of such systems. We investigate methods and concepts for the provision of “sound” assemblies. We define an abstract, dynamic, multi-threaded, component model, encompassing both client/server and peer to peer communication patterns. We define a behavioural interface type language endowed with a (Decidable) Set of interface compatibilty rules. Based on the notion of compliance of components to their interfaces, we define the concepts of “contract” and “contract satisfaction”. This leads to the notion of sound assemblies of components, i.e., assemblies made of contracted components interacting through compatible interfaces. Sound assemblies possess interesting properties like “external deadlock freeness” and “message consumption”.
Cyril Carrez - One of the best experts on this subject based on the ideXlab platform.
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Assembling components with behavioural contracts
Annales Des Télécommunications, 2005Co-Authors: Cyril Carrez, Alessandro Fantechi, Elie NajmAbstract:Component based design is a new paradigm to build distributed systems and applications. The problem of compositional verification of such systems is however still open. We investigate methods and concepts for the provision of “sound” assemblies. We define a behavioural interface type language endowed with a (Decidable) Set of interface compatibilty and subtyping rules. We define an abstract, dynamic, multi-threaded, component model, encompassing both client/server and peer to peer communication patterns. Based on the notion of compliance of components to their interfaces, we define the concepts of “contract” and “contract satisfaction”. This leads to sound assemblies of components, which possess interesting properties, such as “external deadlockfreeness” and “message consumption”.
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Assembling components with behavioural contracts
Annales Des Télécommunications, 2005Co-Authors: Cyril Carrez, Alessandro Fantechi, Elie NajmAbstract:La conception basée composants est une nouvelle méthode de construction d’applications et de systèmes distribués. La vérification compositionnelle de ces systèmes reste cependant un problème ouvert. Nous étudions des méthodes et des concepts pour la construction d’assemblages « sains ». Nous définissons un langage de type d’interfaces comportementales, doté d’un ensemble de règles (décidables) de compatibilité d’interface et de sous-typage. Nous définissons un modèle de composant abstrait, dynamique et multi-tâche, qui englobe les modèles client/serveur et point-à-point. Basé sur la notion de conformité du composant par rapport à son interface, nous définissons les concepts de « contrat » et « respect de contrat ». Cela mène aux assemblages sains de composants qui possèdent des propriétés intéressantes, comme «l’absence d’interblocage externe » et «la consommation des messages». Component based design is a new paradigm to build distributed systems and applications. The problem of compositional verification of such systems is however still open. We investigate methods and concepts for the provision of “sound” assemblies. We define a behavioural interface type language endowed with a (Decidable) Set of interface compatibilty and subtyping rules. We define an abstract, dynamic, multi-threaded, component model, encompassing both client/server and peer to peer communication patterns. Based on the notion of compliance of components to their interfaces, we define the concepts of “contract” and “contract satisfaction”. This leads to sound assemblies of components, which possess interesting properties, such as “external deadlockfreeness” and “message consumption”.
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FORTE - Behavioural Contracts for a Sound Assembly of Components
Formal Techniques for Networked and Distributed Systems - FORTE 2003, 2003Co-Authors: Cyril Carrez, Alessandro Fantechi, Elie NajmAbstract:Component based design is a new methodology for the construction of distributed systems and applications. In this new Setting, a system is built by the assembly of (pre)-existing components. Remains the problem of the compositional verification of such systems. We investigate methods and concepts for the provision of “sound” assemblies. We define an abstract, dynamic, multi-threaded, component model, encompassing both client/server and peer to peer communication patterns. We define a behavioural interface type language endowed with a (Decidable) Set of interface compatibilty rules. Based on the notion of compliance of components to their interfaces, we define the concepts of “contract” and “contract satisfaction”. This leads to the notion of sound assemblies of components, i.e., assemblies made of contracted components interacting through compatible interfaces. Sound assemblies possess interesting properties like “external deadlock freeness” and “message consumption”.
Alessandro Fantechi - One of the best experts on this subject based on the ideXlab platform.
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Assembling components with behavioural contracts
Annales Des Télécommunications, 2005Co-Authors: Cyril Carrez, Alessandro Fantechi, Elie NajmAbstract:Component based design is a new paradigm to build distributed systems and applications. The problem of compositional verification of such systems is however still open. We investigate methods and concepts for the provision of “sound” assemblies. We define a behavioural interface type language endowed with a (Decidable) Set of interface compatibilty and subtyping rules. We define an abstract, dynamic, multi-threaded, component model, encompassing both client/server and peer to peer communication patterns. Based on the notion of compliance of components to their interfaces, we define the concepts of “contract” and “contract satisfaction”. This leads to sound assemblies of components, which possess interesting properties, such as “external deadlockfreeness” and “message consumption”.
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Assembling components with behavioural contracts
Annales Des Télécommunications, 2005Co-Authors: Cyril Carrez, Alessandro Fantechi, Elie NajmAbstract:La conception basée composants est une nouvelle méthode de construction d’applications et de systèmes distribués. La vérification compositionnelle de ces systèmes reste cependant un problème ouvert. Nous étudions des méthodes et des concepts pour la construction d’assemblages « sains ». Nous définissons un langage de type d’interfaces comportementales, doté d’un ensemble de règles (décidables) de compatibilité d’interface et de sous-typage. Nous définissons un modèle de composant abstrait, dynamique et multi-tâche, qui englobe les modèles client/serveur et point-à-point. Basé sur la notion de conformité du composant par rapport à son interface, nous définissons les concepts de « contrat » et « respect de contrat ». Cela mène aux assemblages sains de composants qui possèdent des propriétés intéressantes, comme «l’absence d’interblocage externe » et «la consommation des messages». Component based design is a new paradigm to build distributed systems and applications. The problem of compositional verification of such systems is however still open. We investigate methods and concepts for the provision of “sound” assemblies. We define a behavioural interface type language endowed with a (Decidable) Set of interface compatibilty and subtyping rules. We define an abstract, dynamic, multi-threaded, component model, encompassing both client/server and peer to peer communication patterns. Based on the notion of compliance of components to their interfaces, we define the concepts of “contract” and “contract satisfaction”. This leads to sound assemblies of components, which possess interesting properties, such as “external deadlockfreeness” and “message consumption”.
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FORTE - Behavioural Contracts for a Sound Assembly of Components
Formal Techniques for Networked and Distributed Systems - FORTE 2003, 2003Co-Authors: Cyril Carrez, Alessandro Fantechi, Elie NajmAbstract:Component based design is a new methodology for the construction of distributed systems and applications. In this new Setting, a system is built by the assembly of (pre)-existing components. Remains the problem of the compositional verification of such systems. We investigate methods and concepts for the provision of “sound” assemblies. We define an abstract, dynamic, multi-threaded, component model, encompassing both client/server and peer to peer communication patterns. We define a behavioural interface type language endowed with a (Decidable) Set of interface compatibilty rules. Based on the notion of compliance of components to their interfaces, we define the concepts of “contract” and “contract satisfaction”. This leads to the notion of sound assemblies of components, i.e., assemblies made of contracted components interacting through compatible interfaces. Sound assemblies possess interesting properties like “external deadlock freeness” and “message consumption”.
Eric Allender - One of the best experts on this subject based on the ideXlab platform.
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Avoiding Simplicity is Complex
Theory of Computing Systems, 2012Co-Authors: Eric Allender, Holger SpakowskiAbstract:It is a trivial observation that every Decidable Set has strings of length n with Kolmogorov complexity log n + O (1) if it has any strings of length n at all. Things become much more interesting when one asks whether a similar property holds when one considers resource-bounded Kolmogorov complexity. This is the question considered here: Can a feasible Set A avoid accepting strings of low resource-bounded Kolmogorov complexity, while still accepting some (or many) strings of length n ? More specifically, this paper deals with two notions of resource-bounded Kolmogorov complexity: Kt and KNt. The measure Kt was defined by Levin more than three decades ago and has been studied extensively since then. The measure KNt is a nondeterministic analog of Kt. For all strings x , Kt( x )≥KNt( x ); the two measures are polynomially related if and only if NEXP⊆EXP/poly (Allender et al. in J. Comput. Syst. Sci. 77:14–40, 2011 ). Many longstanding open questions in complexity theory boil down to the question of whether there are Sets in P that avoid all strings of low Kt complexity. For example, the EXP vs ZPP question is equivalent to (one version of) the question of whether avoiding simple strings is difficult: (EXP=ZPP if and only if there exist ϵ >0 and a “dense” Set in P having no strings x with Kt( x )≤| x |^ ϵ (Allender et al. in SIAM J. Comput. 35:1467–1493, 2006 )). Surprisingly, we are able to show unconditionally that avoiding simple strings (in the sense of KNt complexity) is difficult. Every dense Set in NP∩coNP contains infinitely many strings x such that KNt( x )≤| x |^ ϵ for every ϵ >0. The proof does not relativize. As an application, we are able to show that if E=NE, then accepting paths for nondeterministic exponential time machines can be found somewhat more quickly than the brute-force upper bound, if there are many accepting paths.
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CiE - Curiouser and curiouser: the link between incompressibility and complexity
Lecture Notes in Computer Science, 2012Co-Authors: Eric AllenderAbstract:This talk centers around some audacious conjectures that attempt to forge firm links between computational complexity classes and the study of Kolmogorov complexity. More specifically, let R denote the Set of Kolmogorov-random strings. Let $\mbox{\rm BPP}$ denote the class of problems that can be solved with negligible error by probabilistic polynomial-time computations, and let $\mbox{\rm NEXP}$ denote the class of problems solvable in nondeterministic exponential time. Conjecture 1. $\mbox{\rm NEXP} = \mbox{\rm NP}^R$. Conjecture 2. $\mbox{\rm BPP}$ is the class of problems non-adaptively polynomial-time reducible to R. These conjectures are not only audacious; they are obviously false! R is not a Decidable Set, and thus it is absurd to suggest that the class of problems reducible to it constitutes a complexity class. The absurdity fades if, for example, we interpret "$\mbox{\rm NP}^R$" to be "the class of problems that are $\mbox{\rm NP}$-Turing reducible to R, no matter which universal machine we use in defining Kolmogorov complexity". The lecture will survey the body of work (some of it quite recent) that suggests that, when interpreted properly, the conjectures may actually be true.
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CiE - Avoiding simplicity is complex
Programs Proofs Processes, 2010Co-Authors: Eric AllenderAbstract:It is a trivial observation that every Decidable Set has strings of length n with Kolmogorov complexity log n + O(1) if it has any strings of length n at all. Things become much more interesting when one asks whether a similar property holds when one considers resource-bounded Kolmogorov complexity. This is the question considered here: Can a feasible Set A avoid accepting strings of low resource-bounded Kolmogorov complexity, while still accepting some (or many) strings of length n?. More specifically, this paper deals with two notions of resource-bounded Kolmogorov complexity: Kt and KNt. The measure Kt was defined by Levin more than three decades ago and has been studied extensively since then. The measure KNt is a nondeterministic analog of Kt. For all strings x, Kt(x) K the two measures are polynomially related if and only if NEXP ⊆ EXP/poly [5]. Many longstanding open questions in complexity theory boil down to the question of whether there are Sets in P that avoid all strings of low Kt complexity. For example, the EXP vs ZPP question is equivalent to (one version of) the question of whether avoiding simple strings is difficult: (EXP = ZPP if and only if there exist e > 0 and a "dense" Set in P having no strings x with Kt(x) = |x|e [4]). Surprisingly, we are able to show unconditionally that avoiding simple strings (in the sense of KNt complexity) is difficult. Every dense Set in NP ∩ co-NP contains infinitely many strings x such that KNt(x) ≤ |x|e for some e. The proof does not relativize. As an application, we are able to show that if E = NE, then accepting paths for nondeterministic exponential time machines can be found somewhat more quickly than the brute-force upper bound, if there are many accepting paths.
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What can be efficiently reduced to the Kolmogorov-random strings?
Annals of Pure and Applied Logic, 2006Co-Authors: Eric Allender, Harry Buhrman, Michal KouckýAbstract:Abstract We investigate the question of whether one can characterize complexity classes (such as PSPACE or NEXP) in terms of efficient reducibility to the Set of Kolmogorov-random strings R C . This question arises because PSPACE ⊆ P R C and NEXP ⊆ NP R C , and no larger complexity classes are known to be reducible to R C in this way. We show that this question cannot be posed without explicitly dealing with issues raised by the choice of universal machine in the definition of Kolmogorov complexity. What follows is a list of some of our main results. • Although Kummer showed that, for every universal machine U there is a time bound t such that the halting problem is disjunctive truth-table reducible to R C U in time t , there is no such time bound t that suffices for every universal machine U . We also show that, for some machines U , the disjunctive reduction can be computed in as little as doubly-exponential time. • Although for every universal machine U , there are very complex Sets that are ≤ dtt P -reducible to R C U , it is nonetheless true that P = REC ∩ ⋂ U { A : A ≤ dtt P R C U } . (A similar statement holds for parity-truth-table reductions.) • Any Decidable Set that is polynomial-time monotone-truth-table reducible to R C is in P / poly . • Any Decidable Set that is polynomial-time truth-table reducible to R C via a reduction that asks at most f ( n ) queries on inputs of size n lies in P / ( f ( n ) 2 f ( n ) 3 log f ( n ) ) .
Witold Charatonik - One of the best experts on this subject based on the ideXlab platform.
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CONCUR - On Name Generation and Set-Based Analysis in the Dolev-Yao Model
CONCUR 2002 — Concurrency Theory, 2002Co-Authors: Roberto M. Amadio, Witold CharatonikAbstract:We study the control reachability problem in the Dolev-Yao model of cryptographic protocols when principals are represented by tail recursive processes with generated names. We propose a conservative approximation of the problem by reduction to a non-standard collapsed operational semantics and we introduce checkable syntactic conditions entailing the equivalence of the standard and the collapsed semantics. Then we introduce a conservative and Decidable Set-based analysis of the collapsed operational semantics and we characterize a situation where the analysis is exact.
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On Name Generation and Set-Based Analysis in the Dolev-Yao Model
CONCUR 2002 — Concurrency Theory, 2002Co-Authors: Roberto M. Amadio, Witold CharatonikAbstract:We study the control reachability problem in the Dolev-Yao model of cryptographic protocols when principals are represented by tail recursive processes with generated names. We propose a conservative approximation of the problem by reduction to a non-standard collapsed operational semantics and we introduce checkable syntactic conditions entailing the equivalence of the standard and the collapsed semantics. Then we introduce a conservative and Decidable Set-based analysis of the collapsed operational semantics and we characterize a situation where the analysis is exact.
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On name generation and Set-based analysis in Dolev-Yao model
2002Co-Authors: Roberto M. Amadio, Witold CharatonikAbstract:We study the control reachability problem in the Dolev-Yao model of cryptograp- hic protocols when principals are represented by tail recursive processes with generated names. We propose a conservative approximation of the problem by reduction to a non-standard collapsed operational semantics and we introduce checkable syntactic conditions entailing the equivalence of the standard and the collapsed semantics. Then we introduce a conservative and Decidable Set-based analysis of the collapsed operational semantics and we characterize a situation where the analysis is exact. Finally, we describe how our framework can be used to specify secrecy and freshness properties of cryptographic protocols.
