6,239 research outputs found
Constraint-Based Qualitative Simulation
We consider qualitative simulation involving a finite set of qualitative
relations in presence of complete knowledge about their interrelationship. We
show how it can be naturally captured by means of constraints expressed in
temporal logic and constraint satisfaction problems. The constraints relate at
each stage the 'past' of a simulation with its 'future'. The benefit of this
approach is that it readily leads to an implementation based on constraint
technology that can be used to generate simulations and to answer queries about
them.Comment: 10 pages, to appear at the conference TIME 200
Reasoning about Qualitative Direction and Distance between Extended Objects using Answer Set Programming
In this thesis, we introduce a novel formal framework to represent and reason
about qualitative direction and distance relations between extended objects
using Answer Set Programming (ASP). We take Cardinal Directional Calculus (CDC)
as a starting point and extend CDC with new sorts of constraints which involve
defaults, preferences and negation. We call this extended version as nCDC. Then
we further extend nCDC by augmenting qualitative distance relation and name
this extension as nCDC+. For CDC, nCDC, nCDC+, we introduce an ASP-based
general framework to solve consistency checking problems, address composition
and inversion of qualitative spatial relations, infer unknown or missing
relations between objects, and find a suitable configuration of objects which
fulfills a given inquiry.Comment: In Proceedings ICLP 2019, arXiv:1909.0764
Inductive learning spatial attention
This paper investigates the automatic induction of spatial attention
from the visual observation of objects manipulated
on a table top. In this work, space is represented in terms of
a novel observer-object relative reference system, named Local
Cardinal System, defined upon the local neighbourhood
of objects on the table. We present results of applying the
proposed methodology on five distinct scenarios involving
the construction of spatial patterns of coloured blocks
Reasoning about Cardinal Directions between 3-Dimensional Extended Objects using Answer Set Programming
We propose a novel formal framework (called 3D-nCDC-ASP) to represent and
reason about cardinal directions between extended objects in 3-dimensional (3D)
space, using Answer Set Programming (ASP). 3D-nCDC-ASP extends Cardinal
Directional Calculus (CDC) with a new type of default constraints, and nCDC-ASP
to 3D. 3D-nCDC-ASP provides a flexible platform offering different types of
reasoning: Nonmonotonic reasoning with defaults, checking consistency of a set
of constraints on 3D cardinal directions between objects, explaining
inconsistencies, and inferring missing CDC relations. We prove the soundness of
3D-nCDC-ASP, and illustrate its usefulness with applications. This paper is
under consideration for acceptance in TPLP.Comment: Paper presented at the 36th International Conference on Logic
Programming (ICLP 2020), University Of Calabria, Rende (CS), Italy, September
2020, 29 pages, 6 figure
Algebraic Properties of Qualitative Spatio-Temporal Calculi
Qualitative spatial and temporal reasoning is based on so-called qualitative
calculi. Algebraic properties of these calculi have several implications on
reasoning algorithms. But what exactly is a qualitative calculus? And to which
extent do the qualitative calculi proposed meet these demands? The literature
provides various answers to the first question but only few facts about the
second. In this paper we identify the minimal requirements to binary
spatio-temporal calculi and we discuss the relevance of the according axioms
for representation and reasoning. We also analyze existing qualitative calculi
and provide a classification involving different notions of a relation algebra.Comment: COSIT 2013 paper including supplementary materia
A Generalised Approach for Encoding and Reasoning with Qualitative Theories in Answer Set Programming
Qualitative reasoning involves expressing and deriving knowledge based on
qualitative terms such as natural language expressions, rather than strict
mathematical quantities. Well over 40 qualitative calculi have been proposed so
far, mostly in the spatial and temporal domains, with several practical
applications such as naval traffic monitoring, warehouse process optimisation
and robot manipulation. Even if a number of specialised qualitative reasoning
tools have been developed so far, an important barrier to the wider adoption of
these tools is that only qualitative reasoning is supported natively, when
real-world problems most often require a combination of qualitative and other
forms of reasoning. In this work, we propose to overcome this barrier by using
ASP as a unifying formalism to tackle problems that require qualitative
reasoning in addition to non-qualitative reasoning. A family of ASP encodings
is proposed which can handle any qualitative calculus with binary relations.
These encodings are experimentally evaluated using a real-world dataset based
on a case study of determining optimal coverage of telecommunication antennas,
and compared with the performance of two well-known dedicated reasoners.
Experimental results show that the proposed encodings outperform one of the two
reasoners, but fall behind the other, an acceptable trade-off given the added
benefits of handling any type of reasoning as well as the interpretability of
logic programs. This paper is under consideration for acceptance in TPLP.Comment: Paper presented at the 36th International Conference on Logic
Programming (ICLP 2020), University Of Calabria, Rende (CS), Italy, September
2020, 18 pages, 3 figure
Qualitative Reasoning about Relative Directions : Computational Complexity and Practical Algorithm
Qualitative spatial reasoning (QSR) enables cognitive agents to reason about space using abstract symbols. Among several aspects of space (e.g., topology, direction, distance) directional information is useful for agents navigating in space. Observers typically describe their environment by specifying the relative directions in which they see other objects or other people from their point of view. As such, qualitative reasoning about relative directions, i.e., determining whether a given statement involving relative directions is true, can be advantageously used for applications, for example, robot navigation, computer-aided design and geographical information systems. Unfortunately, despite the apparent importance of reasoning about relative directions, QSR-research so far could not provide efficient decision procedures for qualitative reasoning about relative directions. Accordingly, the question about how to devise an efficient decision procedure for qualitative reasoning about relative directions has meanwhile turned to the question about whether an efficient decision procedure exists at all. Answering the latter existential question, which requires a formal analysis of relative directions from a computational complexity point of view, has remained an open problem in the field of QSR. The present thesis solves the open problem by proving that there is no efficient decision procedure for qualitative reasoning about relative directions, even if only left or right relations are involved. This is surprising as it contradicts the early premise of QSR believed by many researchers in and outside the field, that is, abstracting from an infinite domain to a finite set of relations naturally leads to efficient reasoning. As a consequence of this rather negative result, efficient reasoning with any of the well-known relative direction calculi (OPRAm, DCC, DRA, LR) is impossible. Indeed, the present thesis shows that all the relative direction calculi belong to one and the same class of ∃R-complete problems, which are the problems that can be reduced to the NP-hard decision problem of the existential theory of the reals, and vice versa. Nevertheless, in practice, many interesting computationally hard AI problems can be tackled by means of approximative algorithms and heuristics. In the same vein, the present thesis shows that qualitative reasoning about relative directions can also be tackled with approximative algorithms. In the thesis we develop the qualitative calculus SVm which allows for a practical algorithm for qualitative reasoning about relative directions. SVm also provides an effective semi-decision procedure for the OPRAm calculus, the most versatile one among the relative direction calculi. In this thesis we substantiate the usefulness of SVm by applying it in the marine navigation domain
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