8,978 research outputs found
Folk Theorems on the Correspondence between State-Based and Event-Based Systems
Kripke Structures and Labelled Transition Systems are the two most prominent
semantic models used in concurrency theory. Both models are commonly believed
to be equi-expressive. One can find many ad-hoc embeddings of one of these
models into the other. We build upon the seminal work of De Nicola and
Vaandrager that firmly established the correspondence between stuttering
equivalence in Kripke Structures and divergence-sensitive branching
bisimulation in Labelled Transition Systems. We show that their embeddings can
also be used for a range of other equivalences of interest, such as strong
bisimilarity, simulation equivalence, and trace equivalence. Furthermore, we
extend the results by De Nicola and Vaandrager by showing that there are
additional translations that allow one to use minimisation techniques in one
semantic domain to obtain minimal representatives in the other semantic domain
for these equivalences.Comment: Full version of SOFSEM 2011 pape
Specifying and Analysing SOC Applications with COWS
COWS is a recently defined process calculus for specifying and combining service-oriented applications, while modelling their dynamic behaviour. Since its introduction, a number of methods and tools have been devised to analyse COWS specifications, like e.g. a type system to check confidentiality properties, a logic and a model checker to express and check functional properties of services. In this paper, by means of a case study in the area of automotive systems, we demonstrate that COWS, with some mild linguistic additions, can model all the phases of the life cycle of service-oriented applications, such as publication, discovery, negotiation, orchestration, deployment, reconfiguration and execution. We also provide a flavour of the properties that can be analysed by using the tools mentioned above
A formal approach to autonomic systems programming: the SCEL Language
The autonomic computing paradigm has been proposed to cope with size, complexity and dynamism of contemporary
software-intensive systems. The challenge for language designers is to devise appropriate abstractions
and linguistic primitives to deal with the large dimension of systems, and with their need to
adapt to the changes of the working environment and to the evolving requirements. We propose a set of
programming abstractions that permit to represent behaviors, knowledge and aggregations according to
specific policies, and to support programming context-awareness, self-awareness and adaptation. Based on
these abstractions, we define SCEL (Software Component Ensemble Language), a kernel language whose
solid semantic foundations lay also the basis for formal reasoning on autonomic systems behavior. To show
expressiveness and effectiveness of SCEL’s design, we present a Java implementation of the proposed abstractions
and show how it can be exploited for programming a robotics scenario that is used as a running
example for describing features and potentials of our approac
Towards a Formal Verification Methodology for Collective Robotic Systems
We introduce a UML-based notation for graphically modeling
systems’ security aspects in a simple and intuitive
way and a model-driven process that transforms graphical
specifications of access control policies in XACML. These
XACML policies are then translated in FACPL, a policy
language with a formal semantics, and the resulting policies
are evaluated by means of a Java-based software tool
Classical and Quantum-like approaches to Charged-Particle Fluids in a Quadrupole
A classical description of the dynamics of a dissipative charged-particle
fluid in a quadrupole-like device is developed. It is shown that the set of the
classical fluid equations contains the same information as a complex function
satisfying a Schrodinger-like equation in which Planck's constant is replaced
by the time-varying emittance, which is related to the time-varying temperature
of the fluid. The squared modulus and the gradient of the phase of this complex
function are proportional to the fluid density and to the current velocity,
respectively. Within this framework, the dynamics of an electron bunch in a
storage ring in the presence of radiation damping and quantum-excitation is
recovered. Furthermore, both standard and generalized (including dissipation)
coherent states that may be associated with the classical particle fluids are
fully described in terms of the above formalism.Comment: LaTex, to appear in Physica Script
Variational approach to gravitational theories with two independent connections
A new variational approach for general relativity and modified theories of
gravity is presented. In addition to the metric tensor, two independent affine
connections enter the action as dynamical variables. In the matter action the
dependence upon one of the connections is left completely unspecified. When the
variation is applied to the Einstein-Hilbert action the Einstein field
equations are recovered. However when applied to and Scalar-Tensor
theories, it yields gravitational field equations which differ from their
equivalents obtained with a metric or Palatini variation and reduce to the
former ones only when no connections appear in the matter action.Comment: 11 pages, no figure
Self modulated dynamics of a relativistic charged particle beam in plasma wake field excitation
Self modulated dynamics of a relativistic charged particle beam is reviewed
within the context of the theory of plasma wake field excitation. The
self-consistent description of the beam dynamics is provided by coupling the
Vlasov equation with a Poisson-type equation relating the plasma wake potential
to the beam density. An analysis of the beam envelope self-modulation is then
carried out and the criteria for the occurrence of the instability are
discussed thereby.Comment: This is a 10 pages manuscript which contain 4 figures. This
manuscript is recently submitted in 'Nuclear Instruments and Methods in
Physics Research Section A' as a proceeding of the conference 'EAAC 2015
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