412 research outputs found
pi-calculus, internal mobility, and agent-passing calculi
The -calculus is a process algebra which originates from CCS and permits a natural modelling of mobility (i.e., dynamic reconfigurations of the process linkage) using communication of names. Previous research has shown that the -calculus has much greater expressiveness than CCS, but also a much more complex mathematical theory. The primary goal of this work is to understand the reasons of this gap. Another goal is to compare the expressiveness of {\em \no} calculi, i.e., calculi like -calculus where mobility is achieved via exchange of names, and that of {\em agent-passing calculi}, i.e., calculi where mobility is achieved via exchange of agents. We separate the mobility mechanisms of the \pic into two, respectively called {\em internal mobility} and {\em external mobility}. The study of the subcalculus which only uses internal mobility, called \pii, suggests that internal mobility is responsible for {much} of the expressiveness of the -calculus, whereas external mobility is responsible for {much} of the semantic complications. A pleasant property of \pii is the full symmetry between input and output constructs. Internal mobility is strongly related to agent-passing mobility. By imposing bounds on the order of the types of \pii and of the Higher-Order -calculus \cite{San923} we define a hierarchy of name-passing calculi based on internal mobility and one of agent-passing calculi. We show that there is an exact correspondence, in terms of expressiveness, between the two hierarchies
On the relative expressiveness of higher-order session processes
By integrating constructs from the λ-calculus and the π-calculus, in higher-order process calculi exchanged values may contain processes. This paper studies the relative expressiveness of HOπ, the higher-order π-calculus in which communications are governed by session types. Our main discovery is that HO, a subcalculus of HOπ which lacks name-passing and recursion, can serve as a new core calculus for session-typed higher-order concurrency. By exploring a new bisimulation for HO, we show that HO can encode HOπ fully abstractly (up to typed contextual equivalence) more precisely and efficiently than the first-order session π-calculus (π). Overall, under session types, HOπ, HO, and π are equally expressive; however, HOπ and HO are more tightly related than HOπ and π
On the Computation Power of Name Parameterization in Higher-order Processes
Parameterization extends higher-order processes with the capability of
abstraction (akin to that in lambda-calculus), and is known to be able to
enhance the expressiveness. This paper focuses on the parameterization of
names, i.e. a construct that maps a name to a process, in the higher-order
setting. We provide two results concerning its computation capacity. First,
name parameterization brings up a complete model, in the sense that it can
express an elementary interactive model with built-in recursive functions.
Second, we compare name parameterization with the well-known pi-calculus, and
provide two encodings between them.Comment: In Proceedings ICE 2015, arXiv:1508.0459
Encoding CSP into CCS
We study encodings from CSP into asynchronous CCS with name passing and
matching, so in fact, the asynchronous pi-calculus. By doing so, we discuss two
different ways to map the multi-way synchronisation mechanism of CSP into the
two-way synchronisation mechanism of CCS. Both encodings satisfy the criteria
of Gorla except for compositionality, as both use an additional top-level
context. Following the work of Parrow and Sj\"odin, the first encoding uses a
centralised coordinator and establishes a variant of weak bisimilarity between
source terms and their translations. The second encoding is decentralised, and
thus more efficient, but ensures only a form of coupled similarity between
source terms and their translations.Comment: In Proceedings EXPRESS/SOS 2015, arXiv:1508.0634
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
A Calculus of Mobile Resources
We introduce a calculus of Mobile Resources (MR) tailored for the design and analysis of systems containing mobile, possibly nested, computing devices that may have resource and access constraints, and which are not copyable nor modifiable per se. We provide a reduction as well as a labelled transition semantics and prove a correspondence be- tween barbed bisimulation congruence and a higher-order bisimulation. We provide examples of the expressiveness of the calculus, and apply the theory to prove one of its characteristic properties
Musings on Encodings and Expressiveness
This paper proposes a definition of what it means for one system description
language to encode another one, thereby enabling an ordering of system
description languages with respect to expressive power. I compare the proposed
definition with other definitions of encoding and expressiveness found in the
literature, and illustrate it on a case study: comparing the expressive power
of CCS and CSP.Comment: In Proceedings EXPRESS/SOS 2012, arXiv:1208.244
A Fully Abstract Symbolic Semantics for Psi-Calculi
We present a symbolic transition system and bisimulation equivalence for
psi-calculi, and show that it is fully abstract with respect to bisimulation
congruence in the non-symbolic semantics.
A psi-calculus is an extension of the pi-calculus with nominal data types for
data structures and for logical assertions representing facts about data. These
can be transmitted between processes and their names can be statically scoped
using the standard pi-calculus mechanism to allow for scope migrations.
Psi-calculi can be more general than other proposed extensions of the
pi-calculus such as the applied pi-calculus, the spi-calculus, the fusion
calculus, or the concurrent constraint pi-calculus.
Symbolic semantics are necessary for an efficient implementation of the
calculus in automated tools exploring state spaces, and the full abstraction
property means the semantics of a process does not change from the original
On the Power of Name-Passing Communication
It is shown that generally higher order process calculi cannot be interpreted in name-passing calculi in a robust way
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