76,249 research outputs found
The Event Calculus Assessed
The range of applicability of the Full Event Calculus is proven to be the Ksp-IA class in the Features and Fluents taxonomy. The proof is given with respect to the original definition of this preference logic, where no adjustments of the language or reasoning method were necessary. The result implies that the claims on the expressiveness and
problem-solving power of this logic were indeed correct
Using the event calculus for tracking the normative state of contracts
In this work, we have been principally concerned with the representation of contracts so that their normative state may be tracked in an automated fashion over their deployment lifetime. The normative state of a contract, at a particular time, is the aggregation of instances of normative relations that hold between contract parties at that time, plus the current values of contract variables. The effects of contract events on the normative state of a contract are specified using an XML formalisation of the Event Calculus, called ecXML. We use an example mail service agreement from the domain of web services to ground the discussion of our work. We give a characterisation of the agreement according to the normative concepts of: obligation, power and permission, and show how the ecXML representation may be used to track the state of the agreement, according to a narrative of contract events. We also give a description of a state tracking architecture, and a contract deployment tool, both of which have been implemented in the course of our work.
Formal foundations for semantic theories of nominalisation
This paper develops the formal foundations of semantic theories dealing with various kinds of nominalisations. It introduces a combination of an event-calculus with a type-free theory which allows a compositional description to be given of such phenomena like Vendler's distinction between perfect and imperfect nominals, iteration of gerunds and Cresswell's notorious non-urrival of'the train examples. Moreover, the approach argued for in this paper allows a semantic explanation to be given for a wide range of grammatical observations such as the behaviour of certain tpes of nominals with respect to their verbal contexts or the distribution of negation in nominals
On Practical Verification of Processes
The integration of a formal process theory with a practically usable notation is not straightforward, but it is necessary for practical verification of process specifications. Given such an intermediate language, a verification process that gives useful feedback is not trivial either: Model checkers are not powerful enough to deal with object models, and theorem provers provide insu#cient feedback and are not certain to find a proof
An Adynamical, Graphical Approach to Quantum Gravity and Unification
We use graphical field gradients in an adynamical, background independent
fashion to propose a new approach to quantum gravity and unification. Our
proposed reconciliation of general relativity and quantum field theory is based
on a modification of their graphical instantiations, i.e., Regge calculus and
lattice gauge theory, respectively, which we assume are fundamental to their
continuum counterparts. Accordingly, the fundamental structure is a graphical
amalgam of space, time, and sources (in parlance of quantum field theory)
called a "spacetimesource element." These are fundamental elements of space,
time, and sources, not source elements in space and time. The transition
amplitude for a spacetimesource element is computed using a path integral with
discrete graphical action. The action for a spacetimesource element is
constructed from a difference matrix K and source vector J on the graph, as in
lattice gauge theory. K is constructed from graphical field gradients so that
it contains a non-trivial null space and J is then restricted to the row space
of K, so that it is divergence-free and represents a conserved exchange of
energy-momentum. This construct of K and J represents an adynamical global
constraint between sources, the spacetime metric, and the energy-momentum
content of the element, rather than a dynamical law for time-evolved entities.
We use this approach via modified Regge calculus to correct proper distance in
the Einstein-deSitter cosmology model yielding a fit of the Union2 Compilation
supernova data that matches LambdaCDM without having to invoke accelerating
expansion or dark energy. A similar modification to lattice gauge theory
results in an adynamical account of quantum interference.Comment: 47 pages text, 14 figures, revised per recent results, e.g., dark
energy result
On the motivation and foundation of Natural Time Analysis: Useful remarks
Since its introduction in 2001, natural time analysis has been applied to
diverse fields with remarkable results. Its validity has not been doubted by
any publication to date. Here, we indicate that frequently asked questions on
the motivation and the foundation of natural time analysis are directly
answered if one takes into account the following two key points that we have
considered as widely accepted when natural time analysis was proposed: First,
the aspects on the energy of a system forwarded by Max Planck in his Treatise
on Thermodynamics. Second, the theorem on the characteristic functions of
probability distributions which Gauss called Ein Sch\"ones Theorem der
Wahrscheinlichkeitsrechnung (beautiful theorem of probability calculus). The
case of the time series of earthquakes and of the precursory Seismic Electric
Signals are discussed as typical examples.Comment: 17 pages including 1 figure. Accepted for publication in Acta
Geophysica on May 1, 201
Formal security analysis of registration protocols for interactive systems: a methodology and a case of study
In this work we present and formally analyze CHAT-SRP (CHAos based
Tickets-Secure Registration Protocol), a protocol to provide interactive and
collaborative platforms with a cryptographically robust solution to classical
security issues. Namely, we focus on the secrecy and authenticity properties
while keeping a high usability. In this sense, users are forced to blindly
trust the system administrators and developers. Moreover, as far as we know,
the use of formal methodologies for the verification of security properties of
communication protocols isn't yet a common practice. We propose here a
methodology to fill this gap, i.e., to analyse both the security of the
proposed protocol and the pertinence of the underlying premises. In this
concern, we propose the definition and formal evaluation of a protocol for the
distribution of digital identities. Once distributed, these identities can be
used to verify integrity and source of information. We base our security
analysis on tools for automatic verification of security protocols widely
accepted by the scientific community, and on the principles they are based
upon. In addition, it is assumed perfect cryptographic primitives in order to
focus the analysis on the exchange of protocol messages. The main property of
our protocol is the incorporation of tickets, created using digests of chaos
based nonces (numbers used only once) and users' personal data. Combined with a
multichannel authentication scheme with some previous knowledge, these tickets
provide security during the whole protocol by univocally linking each
registering user with a single request. [..]Comment: 32 pages, 7 figures, 8 listings, 1 tabl
Implementing a distributed mobile calculus using the IMC framework
In the last decade, many calculi for modelling distributed mobile code have been proposed. To assess their merits and encourage use, implementations of the calculi have often been proposed. These implementations usually consist of a limited part dealing with mechanisms that are specific of the proposed calculus and of a significantly larger part handling recurrent mechanisms that are common to many calculi. Nevertheless, also the "classic" parts are often re-implemented from scratch. In this paper we show how to implement a well established representative of the family of mobile calculi, the distributed [pi]-calculus, by using a Java middleware (called IMC - Implementing Mobile Calculi) where recurrent mechanisms of distributed and mobile systems are already implemented. By means of the case study, we illustrate a methodology to accelerate the development of prototype implementations while concentrating only on the features that are specific of the calculus under consideration and relying on the common framework for all the recurrent mechanisms like network connections, code mobility, name handling, etc
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