578 research outputs found
KLAIM: A Kernel Language for Agents Interaction and Mobility
We investigate the issue of designing a kernel programming language for mobile computing and describe KLAIM, a language that supports a programming paradigm where processes, like data, can be moved from one computing environment to another. The language consists of a core Linda with multiple tuple spaces and of a set of operators for building processes. KLAIM naturally supports programming with explicit localities. Localities are first-class data (they can be manipulated like any other data), but the language provides coordination mechanisms to control the interaction protocols among located processes. The formal operational semantics is useful for discussing the design of the language and provides guidelines for implementations. KLAIM is equipped with a type system that statically checks access rights violations of mobile agents. Types are used to describe the intentions (read, write, execute, etc.) of processes in relation to the various localities. The type system is used to determine the operations that processes want to perform at each locality, and to check whether they comply with the declared intentions and whether they have the necessary rights to perform the intended operations at the specific localities. Via a series of examples, we show that many mobile code programming paradigms can be naturally implemented in our kernel language. We also present a prototype implementaton of KLAIM in Java
Towards a Formal Framework for Mobile, Service-Oriented Sensor-Actuator Networks
Service-oriented sensor-actuator networks (SOSANETs) are deployed in
health-critical applications like patient monitoring and have to fulfill strong
safety requirements. However, a framework for the rigorous formal modeling and
analysis of SOSANETs does not exist. In particular, there is currently no
support for the verification of correct network behavior after node failure or
loss/addition of communication links. To overcome this problem, we propose a
formal framework for SOSANETs. The main idea is to base our framework on the
\pi-calculus, a formally defined, compositional and well-established formalism.
We choose KLAIM, an existing formal language based on the \pi-calculus as the
foundation for our framework. With that, we are able to formally model SOSANETs
with possible topology changes and network failures. This provides the basis
for our future work on prediction, analysis and verification of the network
behavior of these systems. Furthermore, we illustrate the real-life
applicability of this approach by modeling and extending a use case scenario
from the medical domain.Comment: In Proceedings FESCA 2013, arXiv:1302.478
Analysing Mutual Exclusion using Process Algebra with Signals
In contrast to common belief, the Calculus of Communicating Systems (CCS) and
similar process algebras lack the expressive power to accurately capture mutual
exclusion protocols without enriching the language with fairness assumptions.
Adding a fairness assumption to implement a mutual exclusion protocol seems
counter-intuitive. We employ a signalling operator, which can be combined with
CCS, or other process calculi, and show that this minimal extension is
expressive enough to model mutual exclusion: we confirm the correctness of
Peterson's mutual exclusion algorithm for two processes, as well as Lamport's
bakery algorithm, under reasonable assumptions on the underlying memory model.
The correctness of Peterson's algorithm for more than two processes requires
stronger, less realistic assumptions on the underlying memory model.Comment: In Proceedings EXPRESS/SOS 2017, arXiv:1709.0004
Mobile Applications in X-KLAIM
Networking has turned computers from isolated data
processors into powerful communication and elaboration
devices, called global computers; an illustrative example is
the WorldâWide Web. Global computers are rapidly evolving
towards programmability. The new scenario has called
for new programming languages and paradigms centered
around the notions of mobility and location awareness. In
this paper, we briefly present X-KLAIM, an experimental
programming language for global computers, and show a
few programming examples
Local and Global Properties of the World
The essence of the method of physics is inseparably connected with the
problem of interplay between local and global properties of the universe. In
the present paper we discuss this interplay as it is present in three major
departments of contemporary physics: general relativity, quantum mechanics and
some attempts at quantizing gravity (especially geometrodynamics and its recent
successors in the form of various pregeometry conceptions). It turns out that
all big interpretative issues involved in this problem point towards the
necessity of changing from the standard space-time geometry to some radically
new, most probably non-local, generalization. We argue that the recent
noncommutative geometry offers attractive possibilities, and gives us a
conceptual insight into its algebraic foundations. Noncommutative spaces are,
in general, non-local, and their applications to physics, known at present,
seem very promising. One would expect that beneath the Planck threshold there
reigns a ``noncommutative pregeometry'', and only when crossing this threshold
the usual space-time geometry emerges.Comment: 43 pages, latex, no figures, changes: authors and abstract added to
the body of pape
From Process Calculi to Klaim and Back
We briefly describe the motivations and the background behind the design of Klaim, a process description language that has proved to be suitable for describing a wide range of distributed applications with agents and code mobility. We argue that a drawback of Klaim is that it is neither a programming language, nor a process calculus. We then outline the two research directions we have pursued more recently. On the one hand we have evolved Klaim to a full-fledged language for distributed mobile programming. On the other hand we have distilled the language into a number of simple calculi that we have used to define new semantic theories and equivalences and to test the impact of new operators for network aware programming
Higher-Spin Interactions: four-point functions and beyond
In this work we construct an infinite class of four-point functions for
massless higher-spin fields in flat space that are consistent with the gauge
symmetry. In the Lagrangian picture, these reflect themselves in a peculiar
non-local nature of the corresponding non-abelian higher-spin couplings implied
by the Noether procedure that starts from the fourth order. We also comment on
the nature of the colored spin-2 excitation present both in the open string
spectrum and in the Vasiliev system, highlighting how some aspects of String
Theory appear to reflect key properties of Field Theory that go beyond its low
energy limit. A generalization of these results to n-point functions, fermions
and mixed-symmetry fields is also addressed.Comment: 66 pages, 10 figures, 1 table, LaTex. Several statements clarified.
Final version to appear in JHE
T-Duality in Arbitrary String Backgrounds
T-Duality is a poorly understood symmetry of the space-time fields of string
theory that interchanges long and short distances. It is best understood in the
context of toroidal compactification where, loosely speaking, radii of the
torus are inverted. Even in this case, however, conventional techniques permit
an understanding of the transformations only in the case where the metric on
the torus is endowed with Abelian Killing symmetries. Attempting to apply these
techniques to a general metric appears to yield a non-local world-sheet theory
that would defy interpretation in terms of space-time fields. However, there is
now available a simple but powerful general approach to understanding the
symmetry transformations of string theory, which are generated by certain
similarity transformations of the stress-tensors of the associated conformal
field theories. We apply this method to the particular case of T-Duality and i)
rederive the known transformations, ii) prove that the problem of non-locality
is illusory, iii) give an explicit example of the transformation of a metric
that lacks Killing symmetries and iv) derive a simple transformation rule for
arbitrary string fields on tori.Comment: 25 pages, plain Tex, new references adde
Location equivalence in a parametric setting
AbstractLocation equivalence has been presented in [5] as a bisimulation-based equivalence able to take into account the spatial distribution of processes.In this work, the parametric approach of [12] is applied to location equivalence. An observation domain for localities is identified and the associated equivalence is shown to coincide with the equivalence introducted in [6,16]. The observation of a computation is a forest (defined up to isomorphism) whose nodes are the events (labeled by observable actions) and where the arcs describe the sublocation relation.We show in the paper that our approach is really parametric. By performing minor changes in the definitions, many equivalences are captured: partial and mixed ordering causal semantics, interleaving, and a variation of location equivalence where the generation ordering is not evidenced. It seems difficult to modify the definitions of [6,16] to obtain the last observation. The equivalence induced by this observation corresponds to the very intuitive assumption that different locations cannot share a common clock, and hence the ordering between events occurring in different places cannot be determined.Thanks to the general results proved in [12] for the parametric approach, all the observation equivalences described in this paper come equipped with sound and complete axiomatizations
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