11,526 research outputs found
A Max-Plus Model of Asynchronous Cellular Automata
This paper presents a new framework for asynchrony. This has its origins in
our attempts to better harness the internal decision making process of cellular
automata (CA). Thus, we show that a max-plus algebraic model of asynchrony
arises naturally from the CA requirement that a cell receives the state of each
neighbour before updating. The significant result is the existence of a
bijective mapping between the asynchronous system and the synchronous system
classically used to update cellular automata. Consequently, although the CA
outputs look qualitatively different, when surveyed on "contours" of real time,
the asynchronous CA replicates the synchronous CA. Moreover, this type of
asynchrony is simple - it is characterised by the underlying network structure
of the cells, and long-term behaviour is deterministic and periodic due to the
linearity of max-plus algebra. The findings lead us to proffer max-plus algebra
as: (i) a more accurate and efficient underlying timing mechanism for models of
patterns seen in nature, and (ii) a foundation for promising extensions and
applications.Comment: in Complex Systems (Complex Systems Publications Inc), Volume 23,
Issue 4, 201
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
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
Markov two-components processes
We propose Markov two-components processes (M2CP) as a probabilistic model of
asynchronous systems based on the trace semantics for concurrency. Considering
an asynchronous system distributed over two sites, we introduce concepts and
tools to manipulate random trajectories in an asynchronous framework: stopping
times, an Asynchronous Strong Markov property, recurrent and transient states
and irreducible components of asynchronous probabilistic processes. The
asynchrony assumption implies that there is no global totally ordered clock
ruling the system. Instead, time appears as partially ordered and random. We
construct and characterize M2CP through a finite family of transition matrices.
M2CP have a local independence property that guarantees that local components
are independent in the probabilistic sense, conditionally to their
synchronization constraints. A synchronization product of two Markov chains is
introduced, as a natural example of M2CP.Comment: 34 page
Issues about the Adoption of Formal Methods for Dependable Composition of Web Services
Web Services provide interoperable mechanisms for describing, locating and
invoking services over the Internet; composition further enables to build
complex services out of simpler ones for complex B2B applications. While
current studies on these topics are mostly focused - from the technical
viewpoint - on standards and protocols, this paper investigates the adoption of
formal methods, especially for composition. We logically classify and analyze
three different (but interconnected) kinds of important issues towards this
goal, namely foundations, verification and extensions. The aim of this work is
to individuate the proper questions on the adoption of formal methods for
dependable composition of Web Services, not necessarily to find the optimal
answers. Nevertheless, we still try to propose some tentative answers based on
our proposal for a composition calculus, which we hope can animate a proper
discussion
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