9,444 research outputs found
Epistemic Logic for Communication Chains
The paper considers epistemic properties of linear communication chains. It
describes a sound and complete logical system that, in addition to the standard
axioms of S5 in a multi-modal language, contains two non-trivial axioms that
capture the linear structure of communication chains.Comment: 7 pages, Contributed talk at TARK 2013 (arXiv:1310.6382)
http://www.tark.or
Inductive Logic Programming in Databases: from Datalog to DL+log
In this paper we address an issue that has been brought to the attention of
the database community with the advent of the Semantic Web, i.e. the issue of
how ontologies (and semantics conveyed by them) can help solving typical
database problems, through a better understanding of KR aspects related to
databases. In particular, we investigate this issue from the ILP perspective by
considering two database problems, (i) the definition of views and (ii) the
definition of constraints, for a database whose schema is represented also by
means of an ontology. Both can be reformulated as ILP problems and can benefit
from the expressive and deductive power of the KR framework DL+log. We
illustrate the application scenarios by means of examples. Keywords: Inductive
Logic Programming, Relational Databases, Ontologies, Description Logics, Hybrid
Knowledge Representation and Reasoning Systems. Note: To appear in Theory and
Practice of Logic Programming (TPLP).Comment: 30 pages, 3 figures, 2 tables
Model Theory for a Compact Cardinal
We would like to develop model theory for T, a complete theory in
L_{theta,theta}(tau) when theta is a compact cardinal. We already have bare
bones stability theory and it seemed we can go no further. Dealing with
ultrapowers (and ultraproducts) naturally we restrict ourselves to "D a
theta-complete ultrafilter on I, probably (I,theta)-regular". The basic
theorems of model theory work and can be generalized (like Los theorem), but
can we generalize deeper parts of model theory? The first section tries to sort
out what occurs to the notion of stable T for complete L_{theta,theta}-theories
T. We generalize several properties of complete first order T, equivalent to
being stable (see [Sh:c]) and find out which implications hold and which fail.
In particular, can we generalize stability enough to generalize [Sh:c, Ch. VI]?
Let us concentrate on saturation in the local sense (types consisting of
instances of one formula). We prove that at least we can characterize the T's
(of cardinality < theta for simplicity) which are minimal for appropriate
cardinal lambda > 2^kappa +|T| in each of the following two senses. One is
generalizing Keisler order which measures how saturated are ultrapowers.
Another asks: Is there an L_{theta,theta}-theory T_1 supseteq T of cardinality
|T| + 2^theta such that for every model M_1 of T_1 of cardinality > lambda, the
tau(T)-reduct M of M_1 is lambda^+-saturated. Moreover, the two versions of
stable used in the characterization are different
Implementing Default and Autoepistemic Logics via the Logic of GK
The logic of knowledge and justified assumptions, also known as logic of
grounded knowledge (GK), was proposed by Lin and Shoham as a general logic for
nonmonotonic reasoning. To date, it has been used to embed in it default logic
(propositional case), autoepistemic logic, Turner's logic of universal
causation, and general logic programming under stable model semantics. Besides
showing the generality of GK as a logic for nonmonotonic reasoning, these
embeddings shed light on the relationships among these other logics. In this
paper, for the first time, we show how the logic of GK can be embedded into
disjunctive logic programming in a polynomial but non-modular translation with
new variables. The result can then be used to compute the extension/expansion
semantics of default logic, autoepistemic logic and Turner's logic of universal
causation by disjunctive ASP solvers such as claspD(-2), DLV, GNT and cmodels.Comment: Proceedings of the 15th International Workshop on Non-Monotonic
Reasoning (NMR 2014
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