1,403 research outputs found
A Logic-based Approach for Recognizing Textual Entailment Supported by Ontological Background Knowledge
We present the architecture and the evaluation of a new system for
recognizing textual entailment (RTE). In RTE we want to identify automatically
the type of a logical relation between two input texts. In particular, we are
interested in proving the existence of an entailment between them. We conceive
our system as a modular environment allowing for a high-coverage syntactic and
semantic text analysis combined with logical inference. For the syntactic and
semantic analysis we combine a deep semantic analysis with a shallow one
supported by statistical models in order to increase the quality and the
accuracy of results. For RTE we use logical inference of first-order employing
model-theoretic techniques and automated reasoning tools. The inference is
supported with problem-relevant background knowledge extracted automatically
and on demand from external sources like, e.g., WordNet, YAGO, and OpenCyc, or
other, more experimental sources with, e.g., manually defined presupposition
resolutions, or with axiomatized general and common sense knowledge. The
results show that fine-grained and consistent knowledge coming from diverse
sources is a necessary condition determining the correctness and traceability
of results.Comment: 25 pages, 10 figure
Applying Formal Methods to Networking: Theory, Techniques and Applications
Despite its great importance, modern network infrastructure is remarkable for
the lack of rigor in its engineering. The Internet which began as a research
experiment was never designed to handle the users and applications it hosts
today. The lack of formalization of the Internet architecture meant limited
abstractions and modularity, especially for the control and management planes,
thus requiring for every new need a new protocol built from scratch. This led
to an unwieldy ossified Internet architecture resistant to any attempts at
formal verification, and an Internet culture where expediency and pragmatism
are favored over formal correctness. Fortunately, recent work in the space of
clean slate Internet design---especially, the software defined networking (SDN)
paradigm---offers the Internet community another chance to develop the right
kind of architecture and abstractions. This has also led to a great resurgence
in interest of applying formal methods to specification, verification, and
synthesis of networking protocols and applications. In this paper, we present a
self-contained tutorial of the formidable amount of work that has been done in
formal methods, and present a survey of its applications to networking.Comment: 30 pages, submitted to IEEE Communications Surveys and Tutorial
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Learning from AI : new trends in database technology
Recently some researchers in the areas of database data modelling and knowledge representations in artificial intelligence have recognized that they share many common goals. In this survey paper we show the relationship between database and artificial intelligence research. We show that there has been a tendency for data models to incorporate more modelling techniques developed for knowledge representations in artificial intelligence as the desire to incorporate more application oriented semantics, user friendliness, and flexibility has increased. Increasing the semantics of the representation is the key to capturing the "reality" of the database environment, increasing user friendliness, and facilitating the support of multiple, possibly conflicting, user views of the information contained in a database
Topological Foundations of Cognitive Science
A collection of papers presented at the First International Summer Institute in Cognitive Science, University at Buffalo, July 1994, including the following papers:
** Topological Foundations of Cognitive Science, Barry Smith
** The Bounds of Axiomatisation, Graham White
** Rethinking Boundaries, Wojciech Zelaniec
** Sheaf Mereology and Space Cognition, Jean Petitot
** A Mereotopological Definition of 'Point', Carola Eschenbach
** Discreteness, Finiteness, and the Structure of Topological Spaces, Christopher Habel
** Mass Reference and the Geometry of Solids, Almerindo E. Ojeda
** Defining a 'Doughnut' Made Difficult, N .M. Gotts
** A Theory of Spatial Regions with Indeterminate Boundaries, A.G. Cohn and N.M. Gotts
** Mereotopological Construction of Time from Events, Fabio Pianesi and Achille C. Varzi
** Computational Mereology: A Study of Part-of Relations for Multi-media Indexing, Wlodek Zadrozny and Michelle Ki
On bisimulation and model-checking for concurrent systems with partial order semantics
EP/G012962/1In concurrency theory—the branch of (theoretical) computer science that studies the logical
and mathematical foundations of parallel computation—there are two main formal ways of
modelling the behaviour of systems where multiple actions or events can happen independently
and at the same time: either with interleaving or with partial order semantics.
On the one hand, the interleaving semantics approach proposes to reduce concurrency to the
nondeterministic, sequential computation of the events the system can perform independently.
On the other hand, partial order semantics represent concurrency explicitly by means of an
independence relation on the set of events that the system can execute in parallel; following
this approach, the so-called ‘true concurrency’ approach, independence or concurrency is a
primitive notion rather than a derived concept as in the interleaving framework.
Using interleaving or partial order semantics is, however, more than a matter of taste. In
fact, choosing one kind of semantics over the other can have important implications—both
from theoretical and practical viewpoints—as making such a choice can raise different issues,
some of which we investigate here. More specifically, this thesis studies concurrent systems
with partial order semantics and focuses on their bisimulation and model-checking problems;
the theories and techniques herein apply, in a uniform way, to different classes of Petri nets,
event structures, and transition system with independence (TSI) models.
Some results of this work are: a number of mu-calculi (in this case, fixpoint extensions of
modal logic) that, in certain classes of systems, induce exactly the same identifications as some
of the standard bisimulation equivalences used in concurrency. Secondly, the introduction of
(infinite) higher-order logic games for bisimulation and for model-checking, where the players
of the games are given (local) monadic second-order power on the sets of elements they are
allowed to play. And, finally, the formalization of a new order-theoretic concurrent game
model that provides a uniform approach to bisimulation and model-checking and bridges some
mathematical concepts in order theory with the more operational world of games.
In particular, we show that in all cases the logic games for bisimulation and model-checking
developed in this thesis are sound and complete, and therefore, also determined—even when
considering models of infinite state systems; moreover, these logic games are decidable in the
finite case and underpin novel decision procedures for systems verification.
Since the mu-calculi and (infinite) logic games studied here generalise well-known fixpoint
modal logics as well as game-theoretic decision procedures for analysing concurrent systems
with interleaving semantics, this thesis provides some of the groundwork for the design of a
logic-based, game-theoretic framework for studying, in a uniform manner, several concurrent
systems regardless of whether they have an interleaving or a partial order semantics
Verifying temporal properties of systems with applications to petri nets
This thesis provides a powerful general-purpose proof technique for the verification
of systems, whether finite or infinite. It extends the idea of finite local
model-checking, which was introduced by Stirling and Walker: rather than
traversing the entire state space of a model, as is done for model-checking in
the sense of Emerson, Clarke et al. (checking whether a (finite) model satisfies
a formula), local model-checking asks whether a particular state satisfies a formula,
and only explores the nearby states far enough to answer that question.
The technique used was a tableau method, constructing a tableau according to
the formula and the local structure of the model. This tableau technique is here
generalized to the infinite case by considering sets of states, rather than single
states; because the logic used, the propositional modal mu-calculus, separates
simple modal and boolean connectives from powerful fix-point operators (which
make the logic more expressive than many other temporal logics), it is possible
to give a relatively straightforward set of rules for constructing a tableau. Much
of the subtlety is removed from the tableau itself, and put into a relation on the
state space defined by the tableau-the success of the tableau then depends on
the well-foundedness of this relation.
This development occupies the second and third chapters: the second considers
the modal mu-calculus, and explains its power, while the third develops
the tableau technique itself
The generalized tableau technique is exhibited on Petri nets, and various
standard notions from net theory are shown to play a part in the use of the
technique on nets-in particular, the invariant calculus has a major role.
The requirement for a finite presentation of tableaux for infinite systems
raises the question of the expressive power of the mu-calculus. This is studied in
some detail, and it is shown that on reasonably powerful models of computation,
such as Petri nets, the mu-calculus can express properties that are not merely
undecidable, but not even arithmetical.
The concluding chapter discusses some of the many questions still to be
answered, such as the incorporation of formal reasoning within the tableau
system, and the power required of such reasoning
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