71 research outputs found
A Calculus of Mobile Processes, II
AbstractThis is the second of two papers in which we present the π-calculus, a calculus of mobile processes. We provide a detailed presentation of some of the theory of the calculus developed to date, and in particular we establish most of the results stated in the companion paper
An Intensional Concurrent Faithful Encoding of Turing Machines
The benchmark for computation is typically given as Turing computability; the
ability for a computation to be performed by a Turing Machine. Many languages
exploit (indirect) encodings of Turing Machines to demonstrate their ability to
support arbitrary computation. However, these encodings are usually by
simulating the entire Turing Machine within the language, or by encoding a
language that does an encoding or simulation itself. This second category is
typical for process calculi that show an encoding of lambda-calculus (often
with restrictions) that in turn simulates a Turing Machine. Such approaches
lead to indirect encodings of Turing Machines that are complex, unclear, and
only weakly equivalent after computation. This paper presents an approach to
encoding Turing Machines into intensional process calculi that is faithful,
reduction preserving, and structurally equivalent. The encoding is demonstrated
in a simple asymmetric concurrent pattern calculus before generalised to
simplify infinite terms, and to show encodings into Concurrent Pattern Calculus
and Psi Calculi.Comment: In Proceedings ICE 2014, arXiv:1410.701
Closed nominal rewriting and efficiently computable nominal algebra equality
We analyse the relationship between nominal algebra and nominal rewriting,
giving a new and concise presentation of equational deduction in nominal
theories. With some new results, we characterise a subclass of equational
theories for which nominal rewriting provides a complete procedure to check
nominal algebra equality. This subclass includes specifications of the
lambda-calculus and first-order logic.Comment: In Proceedings LFMTP 2010, arXiv:1009.218
On the Expressiveness of Intensional Communication
The expressiveness of communication primitives has been explored in a common
framework based on the pi-calculus by considering four features: synchronism
(asynchronous vs synchronous), arity (monadic vs polyadic data), communication
medium (shared dataspaces vs channel-based), and pattern-matching (binding to a
name vs testing name equality). Here pattern-matching is generalised to account
for terms with internal structure such as in recent calculi like Spi calculi,
Concurrent Pattern Calculus and Psi calculi. This paper explores intensionality
upon terms, in particular communication primitives that can match upon both
names and structures. By means of possibility/impossibility of encodings, this
paper shows that intensionality alone can encode synchronism, arity,
communication-medium, and pattern-matching, yet no combination of these without
intensionality can encode any intensional language.Comment: In Proceedings EXPRESS/SOS 2014, arXiv:1408.127
On the Expressiveness of Joining
The expressiveness of communication primitives has been explored in a common
framework based on the pi-calculus by considering four features: synchronism
(asynchronous vs synchronous), arity (monadic vs polyadic data), communication
medium (shared dataspaces vs channel-based), and pattern-matching (binding to a
name vs testing name equality vs intensionality). Here another dimension
coordination is considered that accounts for the number of processes required
for an interaction to occur. Coordination generalises binary languages such as
pi-calculus to joining languages that combine inputs such as the Join Calculus
and general rendezvous calculus. By means of possibility/impossibility of
encodings, this paper shows coordination is unrelated to the other features.
That is, joining languages are more expressive than binary languages, and no
combination of the other features can encode a joining language into a binary
language. Further, joining is not able to encode any of the other features
unless they could be encoded otherwise.Comment: In Proceedings ICE 2015, arXiv:1508.04595. arXiv admin note:
substantial text overlap with arXiv:1408.145
Measuring the Gain of Reconfigurable Communication
We study the advantages of reconfigurable communication interfaces vs fixed
communication interfaces in the context of asynchronous automata. We study the
extension of asynchronous (Zielonka) automata with reconfigurable communication
interfaces. We show that it is possible to capture languages of automata with
reconfigurable communication interfaces by automata with fixed communication
interfaces. However, this comes at a cost of disseminating communication (and
knowledge) to all agents in a system. Thus, the system is no longer behaving as
a distributed system. We then show that this is unavoidable by describing a
language in which every agent that uses a fixed communication interface either
must be aware of all communication or become irrelevant
Statistical Model Checking of Dynamic Networks of Stochastic Hybrid Automata
In this paper we present a modelling formalism for dynamic networksof stochastic hybrid automata. In particular, our formalism is based on primitivesfor the dynamic creation and termination of hybrid automata components duringthe execution of a system. In this way we allow for natural modelling of conceptssuch as multiple threads found in various programming paradigms, as well as thedynamic evolution of biological systems.We provide a natural stochastic semantics of the modelling formalism based on re-peated output races between the dynamic evolving components of a system. Asspecification language we present a quantified extension of the logic Metric Tempo-ral Logic (MTL). As a main contribution of this paper, the statistical model checkingengine of U PPAAL has been extended to the setting of dynamic networks of hybridsystems and quantified MTL. We demonstrate the usefulness of the extended for-malisms in an analysis of a dynamic version of the well-known Train Gate example,as well as in natural monitoring of a MTL formula, where observations may lead todynamic creation of monitors for sub-formulas
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