12688384
Query-By-Trace: Visual Predicate Specification in Spatio-Temporal Databases
In this paper we propose a visual interface for the specification of predicates to be used in queries on spatio-temporal databases. The approach is based on a visual specification method for temporally changing spatial situations. This extends existing concepts for visual spatial query languages, which are only capable of querying static spatial situations. We outline a preliminary user interface that supports the specification on an intuitive and easily manageable level, and we describe the design of the underlying visual language. The visual notation can be used directly as a visual query interface to spatio-temporal databases, or it can provide predicate specifications that can be integrated into textual query languages leading to heterogeneous languages.
5647940
Topological Predicates Between Vague Spatial Objects
Topological predicates are an important element of database systems that allow manipulation of spatial data. Based on the necessity for such systems to handle uncertainty, we introduce a general mechanism that identifies vague topological predicates. This definition forms part of a formal data model referred to as VASA (Vague Spatial Algebra), in which the data types vague regions, vague lines, and vague points are defined in terms of existing definition of crisp spatial data types. Following this trend, the mechanism presented here identifies vague topological predicates on the basis of well defined crisp topological predicates. An example implementation of the mechanism for vague regions is given.
7000612
Implementation of the ROSE Algebra: Efficient Algorithms for Realm-Based Spatial Data Types
The ROSE algebra, defined earlier, is a system of spatial data types for use in spatial database systems. It offers data types to represent points, lines, and regions in the plane together with a comprehensive set of operations; semantics of types and operations have been formally defined. Values of these data types have a quite general structure, e.g. an object of type regions may consist of several polygons with holes. All ROSE objects are realm-based which means all points and vertices of objects lie on an integer grid and no two distinct line segments of any two objects intersect in their interior. In this paper we describe the implementation of the ROSE algebra, providing data structures for the types and new realm-based geometric algorithms for the operations. The main techniques used are (parallel) traversal of objects, plane-sweep, and graph algorithms. All algorithms are analyzed with respect to their worst case time and space requirements. Due to the realm properties, these algorithms are relatively simple, efficient, and numerically completely robust. All data structures and algorithms have indeed been implemented in the ROSE system; the Modula-2 source code is freely available from the authors for study or use.
12076841
Dimension-refined topological predicates
Topological predicates, as derived from the 9-intersection model, have been widely recognized in GIS, spatial database systems, and many other geo-related disciplines. They are based on the evaluation of nine Boolean predicates checking the intersections of the boundary, interior, and exterior of a spatial object with the respective parts of another spatial object for inequality to the empty set. In this paper, we replace each Boolean predicate, which is a topological invariant, by another topological invariant. This new invariant is given as a function yielding the dimension of the respective intersection in the 9-intersection matrix, resulting in a dimension matrix. The goal of this paper is to determine the definition and semantics of all predicates that can be derived from this matrix for all combinations of spatial data types. It turns out that these dimension-based predicates are special refinements of the aforementioned topological predicates; hence, we call them dimension-refined topological predicates. We show that these predicates allow us to pose a class of more fine-grained topological queries.
41544599
RDF: Stores - A Lightweight Approach on Managing Shared Knowledge
One of the central ideas of ubiquitous computing research is to create smart real-world artifacts and environments that can spontaneously cooperate in order to enable novel applications that no single device could provide. A critical factor in such applications is the availability of relevant context knowledge, which may be provided by a variety of different sensors, domain models, and applications. Locating, accessing, and preserving such knowledge is not a trivial task, especially in dynamic environments where new knowledge sources and applications may unexpectedly appear while existing ones may vanish. In this paper we present a pragmatic yet powerful approach to manage shared knowledge by introducing a novel concept called RDF:Stores. We will present the general properties of RDF:Stores and describe how they can be implemented using off-the-shelf software components.
14259556
SearchLight - A Lightweight Search Function for Pervasive Environments
We present a lightweight search function for physical objects in instrumented environments. Objects are tagged with optical markers which are scanned by a steerable camera and projector unit on the ceiling. The same projector can then highlight the objects when given the corresponding marker ID. The process is very robust regarding calibration, and no 3D model of the environment is needed. We discuss the scenario of finding books in a library or office environment and several extensions currently under development.