27,970 research outputs found
Super Logic Programs
The Autoepistemic Logic of Knowledge and Belief (AELB) is a powerful
nonmonotic formalism introduced by Teodor Przymusinski in 1994. In this paper,
we specialize it to a class of theories called `super logic programs'. We argue
that these programs form a natural generalization of standard logic programs.
In particular, they allow disjunctions and default negation of arbibrary
positive objective formulas.
Our main results are two new and powerful characterizations of the static
semant ics of these programs, one syntactic, and one model-theoretic. The
syntactic fixed point characterization is much simpler than the fixed point
construction of the static semantics for arbitrary AELB theories. The
model-theoretic characterization via Kripke models allows one to construct
finite representations of the inherently infinite static expansions.
Both characterizations can be used as the basis of algorithms for query
answering under the static semantics. We describe a query-answering interpreter
for super programs which we developed based on the model-theoretic
characterization and which is available on the web.Comment: 47 pages, revised version of the paper submitted 10/200
Combining and Relating Control Effects and their Semantics
Combining local exceptions and first class continuations leads to programs
with complex control flow, as well as the possibility of expressing powerful
constructs such as resumable exceptions. We describe and compare games models
for a programming language which includes these features, as well as
higher-order references. They are obtained by contrasting methodologies: by
annotating sequences of moves with "control pointers" indicating where
exceptions are thrown and caught, and by composing the exceptions and
continuations monads.
The former approach allows an explicit representation of control flow in
games for exceptions, and hence a straightforward proof of definability (full
abstraction) by factorization, as well as offering the possibility of a
semantic approach to control flow analysis of exception-handling. However,
establishing soundness of such a concrete and complex model is a non-trivial
problem. It may be resolved by establishing a correspondence with the monad
semantics, based on erasing explicit exception moves and replacing them with
control pointers.Comment: In Proceedings COS 2013, arXiv:1309.092
FO(FD): Extending classical logic with rule-based fixpoint definitions
We introduce fixpoint definitions, a rule-based reformulation of fixpoint
constructs. The logic FO(FD), an extension of classical logic with fixpoint
definitions, is defined. We illustrate the relation between FO(FD) and FO(ID),
which is developed as an integration of two knowledge representation paradigms.
The satisfiability problem for FO(FD) is investigated by first reducing FO(FD)
to difference logic and then using solvers for difference logic. These
reductions are evaluated in the computation of models for FO(FD) theories
representing fairness conditions and we provide potential applications of
FO(FD).Comment: Presented at ICLP 2010. 16 pages, 1 figur
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