234 research outputs found
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
A criterion for separating process calculi
We introduce a new criterion, replacement freeness, to discern the relative
expressiveness of process calculi. Intuitively, a calculus is strongly
replacement free if replacing, within an enclosing context, a process that
cannot perform any visible action by an arbitrary process never inhibits the
capability of the resulting process to perform a visible action. We prove that
there exists no compositional and interaction sensitive encoding of a not
strongly replacement free calculus into any strongly replacement free one. We
then define a weaker version of replacement freeness, by only considering
replacement of closed processes, and prove that, if we additionally require the
encoding to preserve name independence, it is not even possible to encode a non
replacement free calculus into a weakly replacement free one. As a consequence
of our encodability results, we get that many calculi equipped with priority
are not replacement free and hence are not encodable into mainstream calculi
like CCS and pi-calculus, that instead are strongly replacement free. We also
prove that variants of pi-calculus with match among names, pattern matching or
polyadic synchronization are only weakly replacement free, hence they are
separated both from process calculi with priority and from mainstream calculi.Comment: In Proceedings EXPRESS'10, arXiv:1011.601
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
Analysing and Comparing Encodability Criteria
Encodings or the proof of their absence are the main way to compare process
calculi. To analyse the quality of encodings and to rule out trivial or
meaningless encodings, they are augmented with quality criteria. There exists a
bunch of different criteria and different variants of criteria in order to
reason in different settings. This leads to incomparable results. Moreover it
is not always clear whether the criteria used to obtain a result in a
particular setting do indeed fit to this setting. We show how to formally
reason about and compare encodability criteria by mapping them on requirements
on a relation between source and target terms that is induced by the encoding
function. In particular we analyse the common criteria full abstraction,
operational correspondence, divergence reflection, success sensitiveness, and
respect of barbs; e.g. we analyse the exact nature of the simulation relation
(coupled simulation versus bisimulation) that is induced by different variants
of operational correspondence. This way we reduce the problem of analysing or
comparing encodability criteria to the better understood problem of comparing
relations on processes.Comment: In Proceedings EXPRESS/SOS 2015, arXiv:1508.06347. The Isabelle/HOL
source files, and a full proof document, are available in the Archive of
Formal Proofs, at
http://afp.sourceforge.net/entries/Encodability_Process_Calculi.shtm
Expressiveness of Process Algebras
AbstractWe examine ways to measure expressiveness of process algebras, and recapitulate and compare some related results from the literature
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