570,221 research outputs found
Coalgebraic Semantics for Timed Processes
We give a coalgebraic formulation of timed processes and their operational semantics. We model time by a monoid called a âtime domainâ, and we model processes by âtimed transition systemsâ, which amount to partial monoid actions of the time domain or, equivalently, coalgebras for an âevolution comonad â generated by the time domain. All our examples of time domains satisfy a partial closure property, yielding a distributive law of a monad for total monoid actions over the evolution comonad, and hence a distributive law of the evolution comonad over a dual comonad for total monoid actions. We show that the induced coalgebras are exactly timed transition systems with delay operators. We then integrate our coalgebraic formulation of time qua timed transition systems into Turi and Plotkinâs formulation of structural operational semantics in terms of distributive laws. We combine timing with action via the more general study of the combination of two arbitrary sorts of behaviour whose operational semantics may interact. We give a modular account of the operational semantics for a combination induced by that of each of its components. Our study necessitates the investigation of products of comonads. In particular, we characterise when a monad lifts to the category of coalgebras for a product comonad, providing constructions with which one can readily calculate. Key words: time domains, timed transition systems, evolution comonads, delay operators, structural operational semantics, modularity, distributive laws
Structural operational semantics for stochastic and weighted transition systems
We introduce weighted GSOS, a general syntactic framework to specify well-behaved transition systems where transitions are equipped with weights coming from a commutative monoid. We prove that weighted bisimilarity is a congruence on systems defined by weighted GSOS specifications. We illustrate the flexibility of the framework by instantiating it to handle some special cases, most notably that of stochastic transition systems. Through examples we provide weighted-GSOS definitions for common stochastic operators in the literature
Labelled transition systems as a Stone space
A fully abstract and universal domain model for modal transition systems and
refinement is shown to be a maximal-points space model for the bisimulation
quotient of labelled transition systems over a finite set of events. In this
domain model we prove that this quotient is a Stone space whose compact,
zero-dimensional, and ultra-metrizable Hausdorff topology measures the degree
of bisimilarity such that image-finite labelled transition systems are dense.
Using this compactness we show that the set of labelled transition systems that
refine a modal transition system, its ''set of implementations'', is compact
and derive a compactness theorem for Hennessy-Milner logic on such
implementation sets. These results extend to systems that also have partially
specified state propositions, unify existing denotational, operational, and
metric semantics on partial processes, render robust consistency measures for
modal transition systems, and yield an abstract interpretation of compact sets
of labelled transition systems as Scott-closed sets of modal transition
systems.Comment: Changes since v2: Metadata updat
ATLAS Pixel Detector: Operational Experience and Run-1 to Run-2 Transition
The Pixel Detector of the ATLAS experiment has shown excellent performance
during the whole Run-1 of LHC. Taking advantage of the long shutdown, the
detector was extracted from the experiment and brought to surface, to equip it
with new service quarter panels, to repair modules and to ease installation of
a new innermost layer, the Insertable B-Layer (IBL). An overview of the
operational experience, the refurbishing of the Pixel Detector and of the IBL
project as well as the experience in its construction, integration and
commissioning are described.Comment: presented at VERTEX 2014 - 23rd International Workshop on Vertex
Detectors, Doksy, Czech Republic, 15 Sep 2014. PoS(Vertex2014)00
Non-Equilibrium Phase Transition in an Atomistic Glassformer: the Connection to Thermodynamics
Tackling the low-temperature fate of supercooled liquids is challenging due
to the immense timescales involved, which prevent equilibration and lead to the
operational glass transition. Relating glassy behaviour to an underlying,
thermodynamic phase transition is a long-standing open question in condensed
matter physics. Like experiments, computer simulations are limited by the small
time window over which a liquid can be equilibrated. Here we address the
challenge of low temperature equilibration using trajectory sampling in a
system undergoing a nonequilibrium phase transition. This transition occurs in
trajectory space between the normal supercooled liquid and a glassy state rich
in low-energy geometric motifs. Our results indicate that this transition might
become accessible in equilibrium configurational space at a temperature close
to the so-called Kauzmann temperature, and provide a possible route to unify
dynamical and thermodynamical theories of the glass transition.Comment: accepted in Physical. Rev.
ROSA Analyser: An automatized approach to analyse processes of ROSA
In this work we present the first version of ROSA Analyser, a tool designed
to get closer to a fully automatic process of analysing the behaviour of a
system specified as a process of the Markovian Process Algebra ROSA. In this
first development stage, ROSA Analyser is able to generate the Labelled
Transition System, according to ROSA Operational Semantics.
ROSA Analyser performance starts with the Syntactic Analysis so generating a
layered structure, suitable to then, apply the Operational Semantics Transition
rules in the easier way. ROSA Analyser is able to recognize some states
identities deeper than the Syntactic ones. This is the very first step in the
way to reduce the size of the LTS and then to avoid the state explosion
problem, so making this task more tractable.
For the sake of better illustrating the usefulness of ROSA Analyser, a case
study is also provided within this work.Comment: In Proceedings WS-FMDS 2012, arXiv:1207.1841. Formal model's too
An approach to a real-time distribution system
The requirements of a real-time data distribution system are to provide fast, reliable delivery of data from source to destination with little or no impact to the data source. In this particular case, the data sources are inside an operational environment, the Mission Control Center (MCC), and any workstation receiving data directly from the operational computer must conform to the software standards of the MCC. In order to supply data to development workstations outside of the MCC, it is necessary to use gateway computers that prevent unauthorized data transfer back to the operational computers. Many software programs produced on the development workstations are targeted for real-time operation. Therefore, these programs must migrate from the development workstation to the operational workstation. It is yet another requirement for the Data Distribution System to ensure smooth transition of the data interfaces for the application developers. A standard data interface model has already been set up for the operational environment, so the interface between the distribution system and the application software was developed to match that model as closely as possible. The system as a whole therefore allows the rapid development of real-time applications without impacting the data sources. In summary, this approach to a real-time data distribution system provides development users outside of the MCC with an interface to MCC real-time data sources. In addition, the data interface was developed with a flexible and portable software design. This design allows for the smooth transition of new real-time applications to the MCC operational environment
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