42189866
Episodes in Space: Qualitative Representation and Reasoning Over Spatio-Temporal Objects
There is growing interest in many application domains for the temporal treatment and manipulation of spatially referenced objects. Handling the time dimension in spatial databases can greatly enhance and extend their functionality and usability by offering means of understanding the spatial behaviour in time. Few works, to date, have been directed towards the development of formalisms for representation and reasoning in this domain. In this paper, a new approach is presented for the representation and reasoning over spatio-temporal relationships. The approach is simple and aims to satisfy the requirements of coherency, expressiveness and reasoning power. Consistent behaviours of spatial objects in time are denoted episodes. The topology of the domain is defined by decomposing episodes into representative components and relationships are defined between those components. Spatio-temporal reasoning is achieved by composing the relationships between the object components using constraint networks. New composition tables between simple spatio-temporal regions and between regions and volumes are also derived and used in the reasoning process.
13190855
Conflict resolution in cartographic name placement
Abstract The increasing application of computer cartography in geographical information systems and in professional map production has highlighted the requirement for automatic positioning of cartographic text in a manner that ensures legibility. An important aspect of the implementation of automated name placement is the avoidance of conflict, in particular due to overlap between names, and between names and map features. This paper reviews the automated strategies that have been adopted for conflict resolution. The majority of these may be classified as either iterative or graph-search procedures. In general the problem may be seen as one in which initially trial positions are generated for each of a selected set of names. These trial positions should obey rules relating to text characteristics and to the relationships between names and other map features. Conflict resolution then consists in finding, for each name, a trial position that obeys the cartographic rules governing the relationships between names.
7423994
Computational Perspectives on Map Generalization
9300744
Matching and aligning features in overlayed coverages
1. ABSTRACT The problems caused by locational error when overlaying spatial data from different sources have been recognised for some time, and much research has been directed towards finding solutions. In this paper we present a solution in the form of an algorithm that seeks to match and align semantically equivalent features prior to overlay. It is assumed that, because of locational error, semantically equivalent features will not always be geometrically equivalent. The technique has been developed to assist in the detection of change between multi-date vector-defined data sets. Initial results, obtained by applying our algorithm to land cover data, are presented. 1.1
205571678
A Prolog Rule-Based System for Cartographic Name Placement
Manual name placement is an extremely time consuming task and has been one of the most difficult aspects of the map production process to automate. It is complicated by the large number of rules required for the selection and placement of names. A hybrid Prolog/Fortrau rule-based system is described for placing names on a variety of map types. It uses a set of Prolog primitives for spatial search and name placement operations. The Ordnance Survey's 1:625000 scale digital dataset has been used to illustrate the application of rules for the selection of labels as well as for controlling their size and orientation. The application to other types of maps and diagrams is also briefly described.
16006621
Splitting atoms safely
The aim of this paper is to make a contribution to (compositional) development methods for concurrent programs. In particular, it takes a fresh look at a number of familiar ideas including the problem of interference. Some subtle issues of observability-including granularity-are explored. Based on these points, the paper sets out some requirements for an approach to developing systems by ''splitting atoms safely''.
7190198
Reasoning About Partial Functions in the Formal Development of Programs
Partial functions and operators are used extensively in the formal development of programs and thus development methods have to clarify how to reason about them. There are a number of approaches which cover up the fact that ''First Order Predicate Calculus'' does not handle undefined logical values. There is also at least one specific ''Logic of Partial Functions'' (LPF) which tackles the issue at its root by using a weaker logic. Recently, we have come to realise that LPF fits a particular way of developing programs. This paper explains why LPF is a suitable logic for ''posit and prove'' development and explores some problems that other approaches present.
13361299
A logic covering undefinedness in program proofs
SummaryRecursive definition often results in partial functions; iteration gives rise to programs which may fail to terminate for some imputs. Proofs about such functions or programs should be conducted in logical systems which reflect the possibility of “undefined values”. This paper provides an axiomatization of such a logic together with examples of its use.
26904654
Investigating Atomicity and Observability
6251055
End-User Programming
End-user software development is a growing avocation in every industry and every country. By the middle of the next century, computer literacy and programming skills will be almost as common as reading and writing skills. Almost every knowledge worker in the world will be able to program if he or she sets out to do so. The implications of widespread end-user software are only just beginning to be considered. There are many exciting possibilities and some potential hazards. The time is now at hand to consider business topics such as ownership of end-user applications and liability in cases of significant errors. >