A robot moving through an environment, an interface to a geographical

Abstract. Continuously moving objects are prevalent in many domains. Although there have been attempts to combine both spatial and temporal relationships from a reasoning, a database, as well as from a logical perspective, the question remains how to describe motion adequately within a qualitative calculus. In this paper, a Qualitative Trajectory Calculus (QTC) for representing and reasoning about moving objects in two dimensions is presented. Specific attention is given to a central concept in qualitative reasoning, namely the composition of relations. The so-called composition-rule table is presented, which is a neat way of representing a composition table. The usefulness of QTC and the composition-rule table is illustrated by an example. 1

ABSTRACT. We analyze and compare geometrical theories based on mereology (mereogeometries). Most theories in this area lack in formalization and this prevents any systematic logical analysis. To overcome this problem, we concentrate on specific interpretations for the primitives and use these to isolate comparable models for each theory. Relying on the chosen interpretations, we introduce the notion of environment structure, that is, a minimal structure containing a (sub)structure for each theory. In particular, in the case of mereogeometries, the domain of an environment structure is composed of particular subsets of R n. The comparison of mereogeometrical theories within these environment structures shows dependencies among primitives and provides (relative) definitional equivalences. With one exception, we show that all the theories considered are equivalent in these environment structures. 1

We investigate the computational complexity of spatial logics extended with the means to represent topological connectedness and restrict the number of connected components. In particular, we show that the connectedness constraints can increase complexity from NP to PSpace, ExpTime and, if component counting is allowed, to NExpTime.

This paper gives an isomorphic representation of the subtheories RT − , RT − EC, and RT of Asher and Vieu’s first-order ontology of mereotopology RT0. It corrects and extends previous work on the representation of these mereotopologies. We develop the theory of p-ortholattices – lattices that are both orthocomplemented and pseudocomplemented – and show that the identity (x·y) ∗ = x ∗ +y ∗ defines the natural class of Stonian p-ortholattices. Equivalent conditions for a p-ortholattice to be Stonian are given. The main contribution of the paper consists of a representation theorem for RT − as Stonian p-ortholattices. Moreover, it is shown that the class of models of RT − EC is isomorphic to the non-distributive Stonian p-ortholattices and a representation of RT is given by a set of four algebras of which one need to be a subalgebra of the present model. As corollary we obtain that Axiom (A11) – existence of two externally connected regions – is in fact a theorem of the remaining axioms of RT.

Abstract. Qualitative spatial and temporal calculi are usually formulated on a particular level of granularity and with a particular domain of spatial or temporal entities. If the granularity or the domain of an existing calculus doesn’t match the requirements of an application, it is either possible to express all information using the given calculus or to customize the calculus. In this paper we distinguish the possible ways of customizing a spatial and temporal calculus and analyze when and how computational properties can be inherited from the original calculus. We present different algorithms for customizing calculi and proof techniques for analyzing their computational properties. We demonstrate our algorithms and techniques on the Interval Algebra for which we obtain some interesting results and observations. We close our paper with results from an empirical analysis which shows that customizing a calculus can lead to a considerably better reasoning performance than using the non-customized calculus. 1

Identifying complexity results for qualitative spatial or temporal calculi has been an important research topic in the past 15 years. Most interesting calculi have been shown to be at least NP-complete, but if tractable fragments of the calculi can be found then efficient reasoning with these calculi is possible. In order to get the most efficient reasoning algorithms, we are interested in identifying maximal tractable fragments of a calculus (tractable fragments such that any extension of the fragment leads to NP-hardness). All required complexity proofs are usually made manually, sometimes using computer assisted enumerations. In a recent paper by Renz (2007), a procedure was presented that automatically identifies tractable fragments of a calculus. In this paper we present an efficient procedure for automatically generating NP-hardness proofs. In order to prove correctness of our procedure, we develop a novel proof method that can be checked automatically and that can be applied to arbitrary spatial and temporal calculi. Up to now, this was believed to be impossible. By combining the two procedures, it is now possible to identify maximal tractable fragments of qualitative spatial and temporal calculi fully automatically.

Models and methods for representing and processing shape semantics

Abstract. Boolean Contact Algebras (BCA) establish the algebraic counterpart of the mereotopolopy induced by the Region Connection Calculus (RCC). Similarly, Stonian p-ortholattices serve as a lattice theoretic version of the ontology RT − of Asher and Vieu. In this paper we study the relationship between BCAs and Stonian p-ortholattices. We show that the skeleton of every Stonian p-ortholattice is a BCA, and, conversely, that every BCA is isomorphic to the skeleton of a Stonian p-ortholattice. Furthermore, we prove the equivalence between algebraic conditions on Stonian p-ortholattices and the axioms C5, C6, and C7 for BCAs. 1

This paper presents a survey of topological spatial logics, taking as its point of departure the interpretation of the modal logic S4 due to McKinsey and Tarski. We consider the effect of extending this logic with the means to represent topological connectedness, focusing principally on the issue of computational complexity. In particular, we draw attention to the special problems which arise when the logics are interpreted not over arbitrary topological spaces, but over (low-dimensional) Euclidean spaces.