6,069 research outputs found
About epistemic negation and world views in Epistemic Logic Programs
In this paper we consider Epistemic Logic Programs, which extend Answer Set
Programming (ASP) with "epistemic operators" and "epistemic negation", and a
recent approach to the semantics of such programs in terms of World Views. We
propose some observations on the existence and number of world views. We show
how to exploit an extended ASP semantics in order to: (i) provide a
characterization of world views, different from existing ones; (ii) query world
views and query the whole set of world views.Comment: Paper presented at the 35th International Conference on Logic
Programming (ICLP 2019), Las Cruces, New Mexico, USA, 20-25 September 2019,
16 page
A survey of advances in epistemic logic program solvers
Recent research in extensions of Answer Set Programming has included a
renewed interest in the language of Epistemic Specifications, which adds modal
operators K ("known") and M ("may be true") to provide for more powerful
introspective reasoning and enhanced capability, particularly when reasoning
with incomplete information. An epistemic logic program is a set of rules in
this language. Infused with the research has been the desire for an efficient
solver to enable the practical use of such programs for problem solving. In
this paper, we report on the current state of development of epistemic logic
program solvers.Comment: Proceedings of the 11th Workshop on Answer Set Programming and Other
Computing Paradigms 201
Revisiting Epistemic Specifications
In 1991, Michael Gelfond introduced the language of epistemic specifications.
The goal was to develop tools for modeling problems that require some form of
meta-reasoning, that is, reasoning over multiple possible worlds. Despite their
relevance to knowledge representation, epistemic specifications have received
relatively little attention so far. In this paper, we revisit the formalism of
epistemic specification. We offer a new definition of the formalism, propose
several semantics (one of which, under syntactic restrictions we assume, turns
out to be equivalent to the original semantics by Gelfond), derive some
complexity results and, finally, show the effectiveness of the formalism for
modeling problems requiring meta-reasoning considered recently by Faber and
Woltran. All these results show that epistemic specifications deserve much more
attention that has been afforded to them so far.Comment: In Marcello Balduccini and Tran Cao Son, Editors, Essays Dedicated to
Michael Gelfond on the Occasion of His 65th Birthday, Lexington, KY, USA,
October 2010, LNAI 6565, Springe
Dynamic Epistemic Logic with ASP Updates: Application to Conditional Planning
Dynamic Epistemic Logic (DEL) is a family of multimodal logics that has
proved to be very successful for epistemic reasoning in planning tasks. In this
logic, the agent's knowledge is captured by modal epistemic operators whereas
the system evolution is described in terms of (some subset of) dynamic logic
modalities in which actions are usually represented as semantic objects called
event models. In this paper, we study a variant of DEL, that wecall DEL[ASP],
where actions are syntactically described by using an Answer Set Programming
(ASP) representation instead of event models. This representation directly
inherits high level expressive features like indirect effects, qualifications,
state constraints, defaults, or recursive fluents that are common in ASP
descriptions of action domains. Besides, we illustrate how this approach can be
applied for obtaining conditional plans in single-agent, partially observable
domains where knowledge acquisition may be represented as indirect effects of
actions
Strong Equivalence for Epistemic Logic Programs Made Easy (Extended Version)
Epistemic Logic Programs (ELPs), that is, Answer Set Programming (ASP)
extended with epistemic operators, have received renewed interest in recent
years, which led to a flurry of new research, as well as efficient solvers. An
important question is under which conditions a sub-program can be replaced by
another one without changing the meaning, in any context. This problem is known
as strong equivalence, and is well-studied for ASP. For ELPs, this question has
been approached by embedding them into epistemic extensions of equilibrium
logics. In this paper, we consider a simpler, more direct characterization that
is directly applicable to the language used in state-of-the-art ELP solvers.
This also allows us to give tight complexity bounds, showing that strong
equivalence for ELPs remains coNP-complete, as for ASP. We further use our
results to provide syntactic characterizations for tautological rules and rule
subsumption for ELPs.Comment: Long version of paper published at AAAI'19, extended with full proof
Knowledge And The Action Description Language A
We introduce Ak, an extension of the action description language A (Gelfond
and Lifschitz, 1993) to handle actions which affect knowledge. We use sensing
actions to increase an agent's knowledge of the world and non-deterministic
actions to remove knowledge. We include complex plans involving conditionals
and loops in our query language for hypothetical reasoning. We also present a
translation of Ak domain descriptions into epistemic logic programs.Comment: Appeared in Theory and Practice of Logic Programming, vol. 1, no. 2,
200
Extending FO(ID) with Knowledge Producing Definitions: Preliminary Results
Previous research into the relation between ASP and classical logic has
identified at least two different ways in which the former extends the latter.
First, ASP program typically contain sets of rules that can be naturally
interpreted as inductive definitions, and the language FO(ID) has shown that
such inductive definitions can elegantly be added to classical logic in a
modular way. Second, there is of course also the well-known epistemic component
of ASP, which was mainly emphasized in the early papers on stable model
semantics. To investigate whether this kind of knowledge can also, and in a
similarly modular way, be added to classical logic, the language of Ordered
Epistemic Logic was presented in recent work. However, this logic views the
epistemic component as entirely separate from the inductive definition
component, thus ignoring any possible interplay between the two. In this paper,
we present a language that extends the inductive definition construct found in
FO(ID) with an epistemic component, making such interplay possible. The
eventual goal of this work is to discover whether it is really appropriate to
view the epistemic component and the inductive definition component of ASP as
two separate extensions of classical logic, or whether there is also something
of importance in the combination of the two.Comment: Proceedings of Answer Set Programming and Other Computing Paradigms
(ASPOCP 2012), 5th International Workshop, September 4, 2012, Budapest,
Hungar
selp: A Single-Shot Epistemic Logic Program Solver
Epistemic Logic Programs (ELPs) are an extension of Answer Set Programming
(ASP) with epistemic operators that allow for a form of meta-reasoning, that
is, reasoning over multiple possible worlds. Existing ELP solving approaches
generally rely on making multiple calls to an ASP solver in order to evaluate
the ELP. However, in this paper, we show that there also exists a direct
translation from ELPs into non-ground ASP with bounded arity. The resulting ASP
program can thus be solved in a single shot. We then implement this encoding
method, using recently proposed techniques to handle large, non-ground ASP
rules, into the prototype ELP solving system "selp", which we present in this
paper. This solver exhibits competitive performance on a set of ELP benchmark
instances. Under consideration in Theory and Practice of Logic Programming
(TPLP).Comment: 19 pages, 2 figures, under consideration in Theory and Practice of
Logic Programming (TPLP
Epistemic Logic Programs: A Different World View
Epistemic Logic Programs (ELPs), an extension of Answer Set Programming (ASP)
with epistemic operators, have received renewed attention from the research
community in recent years. Classically, evaluating an ELP yields a set of world
views, with each being a set of answer sets. In this paper, we propose an
alternative definition of world views that represents them as three-valued
assignments, where each atom can be either always true, always false, or
neither. Based on several examples, we show that this definition is natural and
intuitive. We also investigate relevant computational properties of these new
semantics, and explore how other notions, like strong equivalence, are
affected.Comment: In Proceedings ICLP 2019, arXiv:1909.0764
On Uniform Equivalence of Epistemic Logic Programs
Epistemic Logic Programs (ELPs) extend Answer Set Programming (ASP) with
epistemic negation and have received renewed interest in recent years. This led
to the development of new research and efficient solving systems for ELPs. In
practice, ELPs are often written in a modular way, where each module interacts
with other modules by accepting sets of facts as input, and passing on sets of
facts as output. An interesting question then presents itself: under which
conditions can such a module be replaced by another one without changing the
outcome, for any set of input facts? This problem is known as uniform
equivalence, and has been studied extensively for ASP. For ELPs, however, such
an investigation is, as of yet, missing. In this paper, we therefore propose a
characterization of uniform equivalence that can be directly applied to the
language of state-of-the-art ELP solvers. We also investigate the computational
complexity of deciding uniform equivalence for two ELPs, and show that it is on
the third level of the polynomial hierarchy.Comment: Accepted for publication and presentation at the 35th International
Conference of Logic Programming, ICLP 2019, in Las Cruces, New Mexico, US
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