54,986 research outputs found
Facilitating modular property-preserving extensions of programming languages
We will explore an approach to modular programming language descriptions and extensions in a denotational style.
Based on a language core, language features are added stepwise on the core. Language features can be described
separated from each other in a self-contained, orthogonal way. We present an extension semantics framework consisting
of mechanisms to adapt semantics of a basic language to new structural requirements in an extended language
preserving the behaviour of programs of the basic language. Common templates of extension are provided. These
can be collected in extension libraries accessible to and extendible by language designers. Mechanisms to extend
these libraries are provided. A notation for describing language features embedding these semantics extensions is
presented
Modular Composition of Language Features through Extensions of Semantic Language Models
Today, programming or specification languages are often extended in order to customize them for a particular application domain or to refine the language definition. The extension of a semantic model is often at the centre of such an extension. We will present a framework for linking basic and extended models. The example which we are going to
use is the RSL concurrency model. The RAISE specification language RSL is a formal wide-spectrum specification
language which integrates different features, such as state-basedness, concurrency and modules. The concurrency
features of RSL are based on a refinement of a classical denotational model for process algebras. A modification was
necessary to integrate state-based features into the basic model in order to meet requirements in the design of RSL.
We will investigate this integration, formalising the relationship between the basic model and the adapted version in a rigorous way. The result will be a modular composition of the basic process model and new language features, such as state-based features or input/output. We will show general mechanisms for integration of new features into a language by extending language models in a structured, modular way. In particular, we will concentrate on the preservation of properties of the basic model in these extensions
A thread calculus with molecular dynamics
We present a theory of threads, interleaving of threads, and interaction
between threads and services with features of molecular dynamics, a model of
computation that bears on computations in which dynamic data structures are
involved. Threads can interact with services of which the states consist of
structured data objects and computations take place by means of actions which
may change the structure of the data objects. The features introduced include
restriction of the scope of names used in threads to refer to data objects.
Because that feature makes it troublesome to provide a model based on
structural operational semantics and bisimulation, we construct a projective
limit model for the theory.Comment: 47 pages; examples and results added, phrasing improved, references
replace
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
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
UV dimensional reduction to two from group valued momenta
We describe a new model of deformed relativistic kinematics based on the
group manifold as a four-momentum space. We discuss the
action of the Lorentz group on such space and and illustrate the deformed
composition law for the group-valued momenta. Due to the geometric structure of
the group, the deformed kinematics is governed by {\it two} energy scales
and . A relevant feature of the model is that it exhibits a
running spectral dimension with the characteristic short distance
reduction to found in most quantum gravity scenarios.Comment: 15 pages, 1 figur
The Two-fold Role of Observables in Classical and Quantum Kinematics
Observables have a dual nature in both classical and quantum kinematics: they
are at the same time \emph{quantities}, allowing to separate states by means of
their numerical values, and \emph{generators of transformations}, establishing
relations between different states. In this work, we show how this two-fold
role of observables constitutes a key feature in the conceptual analysis of
classical and quantum kinematics, shedding a new light on the distinguishing
feature of the quantum at the kinematical level. We first take a look at the
algebraic description of both classical and quantum observables in terms of
Jordan-Lie algebras and show how the two algebraic structures are the precise
mathematical manifestation of the two-fold role of observables. Then, we turn
to the geometric reformulation of quantum kinematics in terms of K\"ahler
manifolds. A key achievement of this reformulation is to show that the two-fold
role of observables is the constitutive ingredient defining what an observable
is. Moreover, it points to the fact that, from the restricted point of view of
the transformational role of observables, classical and quantum kinematics
behave in exactly the same way. Finally, we present Landsman's general
framework of Poisson spaces with transition probability, which highlights with
unmatched clarity that the crucial difference between the two kinematics lies
in the way the two roles of observables are related to each other.Comment: Corrected typos; revised final arguments of section 2.2 and added a
figure at the end of this sectio
Massless particles on supergroups and AdS3 x S3 supergravity
Firstly, we study the state space of a massless particle on a supergroup with
a reparameterization invariant action. After gauge fixing the
reparameterization invariance, we compute the physical state space through the
BRST cohomology and show that the quadratic Casimir Hamiltonian becomes
diagonalizable in cohomology. We illustrate the general mechanism in detail in
the example of a supergroup target GL(1|1). The space of physical states
remains an indecomposable infinite dimensional representation of the space-time
supersymmetry algebra. Secondly, we show how the full string BRST cohomology in
the particle limit of string theory on AdS3 x S3 renders the quadratic Casimir
diagonalizable, and reduces the Hilbert space to finite dimensional
representations of the space-time supersymmetry algebra (after analytic
continuation). Our analysis provides an efficient way to calculate the
Kaluza-Klein spectrum for supergravity on AdS3 x S3. It may also be a step
towards the identification of an interesting and simpler subsector of
logarithmic supergroup conformal field theories, relevant to string theory.Comment: 16 pages, 10 figure
Physics of Deformed Special Relativity: Relativity Principle revisited
In many different ways, Deformed Special Relativity (DSR) has been argued to
provide an effective limit of quantum gravity in almost-flat regime. Some
experiments will soon be able to test some low energy effects of quantum
gravity, and DSR is a very promising candidate to describe these latter.
Unfortunately DSR is up to now plagued by many conceptual problems (in
particular how it describes macroscopic objects) which forbids a definitive
physical interpretation and clear predictions. Here we propose a consistent
framework to interpret DSR. We extend the principle of relativity: the same way
that Special Relativity showed us that the definition of a reference frame
requires to specify its speed, we show that DSR implies that we must also take
into account its mass. We further advocate a 5-dimensional point of view on DSR
physics and the extension of the kinematical symmetry from the Poincare group
to the Poincare-de Sitter group (ISO(4,1)). This leads us to introduce the
concept of a pentamomentum and to take into account the renormalization of the
DSR deformation parameter kappa. This allows the resolution of the "soccer ball
problem" (definition of many-particle-states) and provides a physical
interpretation of the non-commutativity and non-associativity of the addition
the relativistic quadrimomentum. In particular, the coproduct of the
kappa-Poincare algebra is interpreted as defining the law of change of
reference frames and not the law of scattering. This point of view places DSR
as a theory, half-way between Special Relativity and General Relativity,
effectively implementing the Schwarzschild mass bound in a flat relativistic
context.Comment: 24 pages, Revtex
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