1,720,997 research outputs found
Intersection types and lambda models
No full textInvariance of interpretation by beta-conversion is one of the minimal requirements for any standard model for the gimel-calculus. With the intersection-type systems being a general framework for the study of semantic domains for the gimel-calculus, the present paper provides a (syntactic) characterisation of the above mentioned requirement in terms of characterisation results for intersection-type assignment systems. Instead of considering conversion as a whole, reduction and expansion will be considered separately. Not only for usual computational rules like beta, eta, but also for a number of relevant restrictions of those. Characterisations will be also provided for (intersection) filter structures that are indeed gimel-models. (c) 2006 Elsevier B.V. All rights reserved
Choreography automata
Full text linkAutomata models are well-established in many areas of computer science and are supported by a wealth of theoretical results including a wide range of algorithms and techniques to specify and analyse systems. We introduce choreography automata for the choreographic modelling of communicating systems. The projection of a choreography automaton yields a system of communicating finite-state machines. We consider both the standard asynchronous semantics of communicating systems and a synchronous variant of it. For both, the projections of well-formed automata are proved to be live as well as lock- and deadlock-free
On Composing Communicating Systems
Full text linkCommunication is an essential element of modern software, yet programming and analysing communicating systems are difficult tasks. A reason for this difficulty is the lack of compositional mechanisms that preserve relevant communication properties. This problem has been recently addressed for the well-known model of communicating systems, that is sets of components consisting of finite-state machines capable of exchanging messages. The main idea of this approach is to take two systems, select a participant from each of them, and derive from those participants a pair of coupled gateways connecting the two systems. More precisely, a message directed to one of the gateways is forwarded to the gateway in the other system, which sends it to the other system. It has been shown that, under some suitable compatibility conditions between gateways, this composition mechanism preserves deadlock freedom for asynchronous as well as symmetric synchronous communications (where sender and receiver play the same part in determining which message to exchange). This paper considers the case of asymmetric synchronous communications where senders decide independently which message should be exchanged. We show here that preservation of lock freedom requires sequentiality of gateways, while this is not needed for preservation of either deadlock freedom or strong lock freedom
A THEORY OF FORMAL CHOREOGRAPHIC LANGUAGES
Full text linkWe introduce a meta-model based on formal languages, dubbed formal choreographic languages, to study message-passing systems. Our framework allows us to generalise standard constructions from the literature and to compare them. In particular, we consider notions such as global view, local view, and projections from the former to the latter. The correctness of local views projected from global views is characterised in terms of a closure property. We consider a number of communication properties –such as (dead)lock-freedom– and give conditions on formal choreographic languages to guarantee them. Finally, we show how formal choreographic languages can capture existing formalisms; specifically we consider communicating finite-state machines, choreography automata, and multiparty session types. Notably, formal choreographic languages, differently from most approaches in the literature, can naturally model systems exhibiting non-regular behaviour
Composition of synchronous communicating systems
Full text linkCommunication is an essential element of modern software, yet programming and analysing communicating systems are difficult tasks. A reason for this difficulty is the lack of compositional mechanisms that preserve relevant communication properties. This problem has been recently addressed for the well-known model of communicating systems, that is sets of components consisting of finite-state machines capable of exchanging messages. Two communicating systems can be composed by selecting one component per system, and transforming both of them into coupled gateways connecting the two systems. More precisely, a gateway forwards a message received from within its system to the other gateway, which then delivers the message to the other system. Suitable compatibility conditions between gateways have been proved sufficient for this composition mechanism to preserve properties such as deadlock freedom for asynchronous as well as symmetric synchronous communications (where sender and receiver play the same part in determining which message to exchange). The present paper gives a comprehensive treatment of the case of synchronous communications. We consider both symmetric synchronous communications and asymmetric synchronous communications (where senders decide independently which message should be exchanged). The composition mechanism preserves different properties under different conditions depending on the considered type of synchronous communication. We show here that preservation of lock freedom requires an additional condition on gateways for asymmetric communication. Such condition is also needed for preservation of deadlock freedom, lock freedom or strong lock freedom for symmetric communications. This is not needed, instead, for preservation of either deadlock freedom or strong lock freedom with asymmetric interactions
Formal Choreographic Languages
Full text linkWe introduce a meta-model based on formal languages, dubbed formal choreographic languages, to study message-passing systems. Our main motivation is to establish a framework for the comparison and generalisation of standard constructions and properties from the literature. In particular, we consider notions such as global view, local view, and projections from the former to the latter. The correctness of local views projected from global views is characterised in terms of a closure property. A condition is also devised to guarantee relevant communication properties such as (dead)lock-freedom. Formal choreographic languages capture existing formalisms for message-passing systems; we detail the cases of multiparty session types and choreography automata. Unlike many other models, formal choreographic languages can naturally model systems exhibiting non-regular behaviour
Composing Communicating Systems, Synchronously
Full text linkCommunicating systems are nowadays part of everyday life, yet programming and analysing them is difficult. One of the many reasons for this difficulty is their size, hence compositional approaches are a need. We discuss how to ensure relevant communication properties such as deadlock freedom in a compositional way. The idea is that communicating systems can be composed by taking two of their participants and transforming them into coupled forwarders connecting the two systems. It has been shown that, for asynchronous communications, if the participants are “compatible” then composition satisfies relevant communication properties provided that the single systems satisfy them. We show that such a result changes considerably for synchronous communications. We also discuss a different form of composition, where a unique forwarder is used
Composition and decomposition of multiparty sessions
Full text linkMultiparty sessions are systems of concurrent processes, which allow several participants to communicate by sending and receiving messages. Their overall behaviour can be described by means of global types. Typable multiparty sessions enjoy lock-freedom. We look at multiparty sessions as open systems by allowing one to compose multiparty sessions by transforming two of their participants into a pair of coupled gateways, forwarding messages between the two sessions. Gateways need to be compatible. We show that the session resulting from the composition can be typed, and its type can be computed from the global types of the starting sessions. As a consequence, lock-freedom is preserved by composition. Compatibility between global types is necessary, since systems obtained by composing sessions with incompatible global types have locks (or they are not sessions). We also define direct composition, which allows one to connect two global types without using gateways. Finally, we propose a decomposition operator, to split a global type into two, which is the left inverse of direct composition. Direct composition and decomposition on global types prepare the ground for a novel framework allowing for the modular design and implementation of distributed systems
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