14,534 research outputs found
Network algebra for synchronous dataflow
We develop an algebraic theory of synchronous dataflow networks. First, a
basic algebraic theory of networks, called BNA (Basic Network Algebra), is
introduced. This theory captures the basic algebraic properties of networks.
For synchronous dataflow networks, it is subsequently extended with additional
constants for the branching connections that occur between the cells of
synchronous dataflow networks and axioms for these additional constants. We
also give two models of the resulting theory, the one based on stream
transformers and the other based on processes as considered in process algebra.Comment: 24 page
Coordination Model and Noninterference
Abstract Noninterference properties for the analysis of secure information flow are proposed in the setting of a process algebra modeling some Linda coordination primitives (asynchronous communication and read operation). To this end, relaxed definitions of equivalence are introduced that take into consideration the observational power of the external observer. The resulting taxonomy is compared with corresponding security definitions for synchronous communication models. As a result, we emphasize how the proposed coordination model affects the expressive power of some noninterference properties, by giving a new intuition to the relative merits
A synchronous program algebra: a basis for reasoning about shared-memory and event-based concurrency
This research started with an algebra for reasoning about rely/guarantee
concurrency for a shared memory model. The approach taken led to a more
abstract algebra of atomic steps, in which atomic steps synchronise (rather
than interleave) when composed in parallel. The algebra of rely/guarantee
concurrency then becomes an instantiation of the more abstract algebra. Many of
the core properties needed for rely/guarantee reasoning can be shown to hold in
the abstract algebra where their proofs are simpler and hence allow a higher
degree of automation. The algebra has been encoded in Isabelle/HOL to provide a
basis for tool support for program verification.
In rely/guarantee concurrency, programs are specified to guarantee certain
behaviours until assumptions about the behaviour of their environment are
violated. When assumptions are violated, program behaviour is unconstrained
(aborting), and guarantees need no longer hold. To support these guarantees a
second synchronous operator, weak conjunction, was introduced: both processes
in a weak conjunction must agree to take each atomic step, unless one aborts in
which case the whole aborts. In developing the laws for parallel and weak
conjunction we found many properties were shared by the operators and that the
proofs of many laws were essentially the same. This insight led to the idea of
generalising synchronisation to an abstract operator with only the axioms that
are shared by the parallel and weak conjunction operator, so that those two
operators can be viewed as instantiations of the abstract synchronisation
operator. The main differences between parallel and weak conjunction are how
they combine individual atomic steps; that is left open in the axioms for the
abstract operator.Comment: Extended version of a Formal Methods 2016 paper, "An algebra of
synchronous atomic steps
A synchronous program algebra: a basis for reasoning about shared-memory and event-based concurrency
This research started with an algebra for reasoning about rely/guarantee
concurrency for a shared memory model. The approach taken led to a more
abstract algebra of atomic steps, in which atomic steps synchronise (rather
than interleave) when composed in parallel. The algebra of rely/guarantee
concurrency then becomes an instantiation of the more abstract algebra. Many of
the core properties needed for rely/guarantee reasoning can be shown to hold in
the abstract algebra where their proofs are simpler and hence allow a higher
degree of automation. The algebra has been encoded in Isabelle/HOL to provide a
basis for tool support for program verification.
In rely/guarantee concurrency, programs are specified to guarantee certain
behaviours until assumptions about the behaviour of their environment are
violated. When assumptions are violated, program behaviour is unconstrained
(aborting), and guarantees need no longer hold. To support these guarantees a
second synchronous operator, weak conjunction, was introduced: both processes
in a weak conjunction must agree to take each atomic step, unless one aborts in
which case the whole aborts. In developing the laws for parallel and weak
conjunction we found many properties were shared by the operators and that the
proofs of many laws were essentially the same. This insight led to the idea of
generalising synchronisation to an abstract operator with only the axioms that
are shared by the parallel and weak conjunction operator, so that those two
operators can be viewed as instantiations of the abstract synchronisation
operator. The main differences between parallel and weak conjunction are how
they combine individual atomic steps; that is left open in the axioms for the
abstract operator.Comment: Extended version of a Formal Methods 2016 paper, "An algebra of
synchronous atomic steps
Design of asynchronous supervisors
One of the main drawbacks while implementing the interaction between a plant
and a supervisor, synthesised by the supervisory control theory of
\citeauthor{RW:1987}, is the inexact synchronisation. \citeauthor{balemiphdt}
was the first to consider this problem, and the solutions given in his PhD
thesis were in the domain of automata theory. Our goal is to address the issue
of inexact synchronisation in a process algebra setting, because we get
concepts like modularity and abstraction for free, which are useful to further
analyze the synthesised system. In this paper, we propose four methods to check
a closed loop system in an asynchronous setting such that it is branching
bisimilar to the modified (asynchronous) closed loop system. We modify a given
closed loop system by introducing buffers either in the plant models, the
supervisor models, or the output channels of both supervisor and plant models,
or in the input channels of both supervisor and plant models. A notion of
desynchronisable closed loop system is introduced, which is a class of
synchronous closed loop systems such that they are branching bisimilar to their
corresponding asynchronous versions. Finally we study different case studies in
an asynchronous setting and then try to summarise the observations (or
conditions) which will be helpful in order to formulate a theory of
desynchronisable closed loop systems
Mastering Heterogeneous Behavioural Models
Heterogeneity is one important feature of complex systems, leading to the
complexity of their construction and analysis. Moving the heterogeneity at
model level helps in mastering the difficulty of composing heterogeneous models
which constitute a large system. We propose a method made of an algebra and
structure morphisms to deal with the interaction of behavioural models,
provided that they are compatible. We prove that heterogeneous models can
interact in a safe way, and therefore complex heterogeneous systems can be
built and analysed incrementally. The Uppaal tool is targeted for
experimentations.Comment: 16 pages, a short version to appear in MEDI'201
Process Algebras
Process Algebras are mathematically rigorous languages with well defined semantics that permit describing and verifying properties of concurrent communicating systems.
They can be seen as models of processes, regarded as agents that act and interact continuously with other similar agents and with their common environment. The agents may be real-world objects (even people), or they may be artifacts, embodied perhaps in computer hardware or software systems.
Many different approaches (operational, denotational, algebraic) are taken for describing the meaning of processes. However, the operational approach is the reference one. By relying on the so called Structural Operational Semantics (SOS), labelled transition systems are built and composed by using the different operators of the many different process algebras. Behavioral equivalences are used to abstract from unwanted details and identify those systems that react similarly to external
experiments
A process algebra for synchronous concurrent constraint programming
Concurrent constraint programming is classically based on asynchronous communication via a shared store. This paper presents new version of the ask and tell primitives which features synchronicity. Our approach is based on the idea of telling new information just in the case that a concurrently running process is asking for it.
An operational and an algebraic semantics are defined. The algebraic semantics is proved to be sound and complete with respect to a compositional operational semantics which is also presented in the paper
Analysis and Verification of Service Interaction Protocols - A Brief Survey
Modeling and analysis of interactions among services is a crucial issue in
Service-Oriented Computing. Composing Web services is a complicated task which
requires techniques and tools to verify that the new system will behave
correctly. In this paper, we first overview some formal models proposed in the
literature to describe services. Second, we give a brief survey of verification
techniques that can be used to analyse services and their interaction. Last, we
focus on the realizability and conformance of choreographies.Comment: In Proceedings TAV-WEB 2010, arXiv:1009.330
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