Results 1  10
of
29
A calculus of mobile processes, I
, 1992
"... We present the acalculus, a calculus of communicating systems in which one can naturally express processes which have changing structure. Not only may the component agents of a system be arbitrarily linked, but a communication between neighbours may carry information which changes that linkage. The ..."
Abstract

Cited by 1184 (31 self)
 Add to MetaCart
We present the acalculus, a calculus of communicating systems in which one can naturally express processes which have changing structure. Not only may the component agents of a system be arbitrarily linked, but a communication between neighbours may carry information which changes that linkage. The calculus is an extension of the process algebra CCS, following work by Engberg and Nielsen, who added mobility to CCS while preserving its algebraic properties. The rrcalculus gains simplicity by removing all distinction between variables and constants; communication links are identified by names, and computation is represented purely as the communication of names across links. After an illustrated description of how the ncalculus generalises conventional process algebras in treating mobility, several examples exploiting mobility are given in some detail. The important examples are the encoding into the ncalculus of higherorder functions (the Icalculus and combinatory algebra), the transmission of processes as values, and the representation of data structures as processes. The paper continues by presenting the algebraic theory of strong bisimilarity and strong equivalence, including a new notion of equivalence indexed by distinctionsi.e., assumptions of inequality among names. These theories are based upon a semantics in terms of a labeled transition system and a notion of strong bisimulation, both of which are expounded in detail in a companion paper. We also report briefly on workinprogress based upon the corresponding notion of weak bisimulation, in which internal actions cannot be observed.
Bigraphs and Mobile Processes (revised)
, 2004
"... A bigraphical reactive system (BRS) involves bigraphs, in which the nesting of nodes represents locality, independently of the edges connecting them; it also allows bigraphs to reconfigure themselves. BRSs aim to provide a uniform way to model spatially distributed systems that both compute and comm ..."
Abstract

Cited by 66 (7 self)
 Add to MetaCart
A bigraphical reactive system (BRS) involves bigraphs, in which the nesting of nodes represents locality, independently of the edges connecting them; it also allows bigraphs to reconfigure themselves. BRSs aim to provide a uniform way to model spatially distributed systems that both compute and communicate. In this memorandum we develop their static and dynamic theory. In Part I we illustrate...
Pure bigraphs: structure and dynamics
, 2005
"... Bigraphs are graphs whose nodes may be nested, representing locality, independently of the edges connecting them. They may be equipped with reaction rules, forming a bigraphical reactive system (Brs) in which bigraphs can reconfigure themselves. Following an earlier paper describing link graphs, a c ..."
Abstract

Cited by 62 (5 self)
 Add to MetaCart
Bigraphs are graphs whose nodes may be nested, representing locality, independently of the edges connecting them. They may be equipped with reaction rules, forming a bigraphical reactive system (Brs) in which bigraphs can reconfigure themselves. Following an earlier paper describing link graphs, a constituent of bigraphs, this paper is a devoted to pure bigraphs, which in turn underlie various more refined forms. Elsewhere it is shown that behavioural analysis for Petri nets, πcalculus and mobile ambients can all be recovered in the uniform framework of bigraphs. The paper first develops the dynamic theory of an abstract structure, a wide reactive system (Wrs), of which a Brs is an instance. In this context, labelled transitions are defined in such a way that the induced bisimilarity is a congruence. This work is then specialised to Brss, whose graphical structure allows many refinements of the theory. The latter part of the paper emphasizes bigraphical theory that is relevant to the treatment of dynamics via labelled transitions. As a running example, the theory is applied to finite pure CCS, whose resulting transition system and bisimilarity are analysed in detail. The paper also mentions briefly the use of bigraphs to model pervasive computing and
Transition systems, link graphs and Petri nets
, 2004
"... A framework is defined within which reactive systems can be studied formally. The framework is based upon scategories, a new variety of categories, within which reactive systems can be set up in such a way that labelled transition systems can be uniformly extracted. These lead in turn to behavi ..."
Abstract

Cited by 29 (5 self)
 Add to MetaCart
A framework is defined within which reactive systems can be studied formally. The framework is based upon scategories, a new variety of categories, within which reactive systems can be set up in such a way that labelled transition systems can be uniformly extracted. These lead in turn to behavioural preorders and equivalences, such as the failures preorder (treated elsewhere) and bisimilarity, which are guaranteed to be congruential. The theory rests upon the notion of relative pushout previously introduced by the authors. The framework
Bigraphical Reactive Systems: Basic Theory
 PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF MATHEMATICIANS
, 2001
"... A notion of bigraph is proposed as the basis for a model of mobile interaction. A bigraph consists of two independent structures: a topograph representing locality and a monograph representing connectivity. Bigraphs are equipped with reaction rules to form bigraphical reactive systems (BRSs), which ..."
Abstract

Cited by 26 (7 self)
 Add to MetaCart
A notion of bigraph is proposed as the basis for a model of mobile interaction. A bigraph consists of two independent structures: a topograph representing locality and a monograph representing connectivity. Bigraphs are equipped with reaction rules to form bigraphical reactive systems (BRSs), which include versions of the calculus and the ambient calculus. Bigraphs are shown to be a special case of a more abstract notion, wide reactive systems (WRSs), not assuming any particular graphical or other structure but equipped with a notion of width, which expresses that agents, contexts and reactions may all be widely distributed entities. A behavioural theory is established for WRSs using the categorical notion of relative pushout; it allows labelled transition systems to be derived uniformly, in such a way that familiar behavioural preorders and equivalences, in particular bisimilarity, are congruential under certain conditions. Then the theory of bigraphs is developed, and they are shown to meet these conditions. It is shown that, using certain functors, other WRSs which meet the conditions may also be derived; these may, for example, be forms of BRS with additional structure. Simple examples of bigraphical systems are discussed; the theory is developed in a number of ways in preparation for deeper application studies.
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 ..."
Abstract

Cited by 16 (2 self)
 Add to MetaCart
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.
Basic Observables for a Calculus for Global Computing
, 2004
"... We develop the semantic theory of a foundational language for modelling applications over global computers whose interconnection structure can be explicitly manipulated. Together with process distribution, process mobility and remote asynchronous communication through distributed data repositories, ..."
Abstract

Cited by 15 (8 self)
 Add to MetaCart
We develop the semantic theory of a foundational language for modelling applications over global computers whose interconnection structure can be explicitly manipulated. Together with process distribution, process mobility and remote asynchronous communication through distributed data repositories, the language provides constructs for explicitly modelling internode connections and for dynamically activating and deactivating them. For the proposed language, we define natural notions of extensional observations and study their closure under operational reductions and/or language contexts to obtain barbed congruence and may testing equivalence. For such equivalences, we provide alternative characterizations in terms of a labelled bisimulation and a trace equivalence that can be used for actual proofs. We discuss how the language and its theory can be extended to include more sophisticated features that enable a finer control on the activation of connections. To asses practical usability of the semantic theory, we model a scenario for communications between mobile devices and use the introduced proof techniques to analyze it and verify some relevant properties.
TAPIDO: Trust and Authorization via Provenance and Integrity in Distributed Objects (Extended Abstract)
"... Existing web services and mashups exemplify the need for flexible construction of distributed applications. How to do so securely remains a topic of current research. We present TAPIDO, a programming model to address Trust and Authorization concerns via Provenance and Integrity in systems of Distrib ..."
Abstract

Cited by 9 (2 self)
 Add to MetaCart
(Show Context)
Existing web services and mashups exemplify the need for flexible construction of distributed applications. How to do so securely remains a topic of current research. We present TAPIDO, a programming model to address Trust and Authorization concerns via Provenance and Integrity in systems of Distributed Objects. Creation of TAPIDO objects requires (static) authorization checks and their communication provides finegrain control of their embedded authorization effects. TAPIDO programs constrain such delegation of rights by using provenance information. A typeandeffect system with effect polymorphism provides static support for the programmer to reason about security policies. We illustrate the programming model and static analysis with example programs and policies.
A Calculus of HigherOrder Distributed Components
 RR4692, INRIA, January, 2003, http://www.inria.fr/rrrt/rr4692.html. Activity Report INRIA 2003 Miscellaneous
"... appor t de re c he rc he ..."
(Show Context)
A PolynomialTime Algorithm for Deciding True Concurrency Equivalences of Basic Parallel Processes
, 2002
"... A polynomialtime algorithm is presented to decide distributed bisimilarity of Basic Parallel Processes. As a direct conclusion, several other noninterleaving semantic equivalences are also decidable in polynomial time for this class of process, since they coincide with distributed bisimilarity. ..."
Abstract

Cited by 6 (1 self)
 Add to MetaCart
A polynomialtime algorithm is presented to decide distributed bisimilarity of Basic Parallel Processes. As a direct conclusion, several other noninterleaving semantic equivalences are also decidable in polynomial time for this class of process, since they coincide with distributed bisimilarity.