17181898
Constraining Inference in an Object-Based Design Model
This paper is the first of a series which are intended to contribute to tractable development methods for concurrent programs by exploring ways in which objectbased language concepts can be used to provide a compositional development method for concurrent programs. The property of a (formal) development method which gives the developmentprocess the potential for productivity is compositionality; interference is what makes it difficult to find compositional development methods for concurrent systems. This paper shows how object-based concepts can be used to provide a designer with control over interference; it also proposes a transformational style of development (for systems with limited interference) in which concurrency is introduced only in the final stages of design. The essential idea here is to show that certain object graphs limit interference.
15308825
Scientific Decisions which Characterize VDM
The formal description and development method known as VDM has been used extensively, its specification language is now an ISO standard, and it has influenced other specification languages. The origins of VDM are normally placed in language description or semantics but it is probably best known in the wider arena of formal methods for (general) program specification and design. This paper sets out a personal view of some of the key technical decisions which characterize the Vienna Development Method.
2399941
Operational semantics: Concepts and their expression
45828501
Formal Definition in Program Development
The intent of the current paper is to show how a large problem like compiler development can be divided in a way which provides a structure for arguments of correctness. Although mechanically checked proofs are not envisaged, the use of formal notation is recommended so that the basis for correctness arguments exists.
6772552
Fixing the semantics of some concurrent object-oriented concepts
Abstract Concurrent object-oriented languages provide a suitable target for a compositional design process that copes with the interference inherent with concurrency. Fixing the semantics of an object-based design language has been undertaken using structured operational semantics and by a mapping to the pi-calculus. These two approaches are outlined and contrasted. In particular, the difficulties in the two approaches of justifying the proof rules of the proposed design method are explained.
9236653
The Early Search for Tractable Ways of Reasoning about Programs
This article traces the history - up to around 1990 - of research on reasoning about programs. The main focus is on sequential imperative programs but some comments are made on concurrency. The main thesis is that the idea of reasoning about programs has been around since they were first written; the search has been to find tractable methods.
7423994
Computational Perspectives on Map Generalization
14219539
Characterisation and generalisation of cartographic lines using Delaunay triangulation
A method is presented for generalising cartographic lines using an approach based on determination of their structure. Constrained Delaunay triangulation is used to construct a skeleton of the space surrounding the lines and hence represent line features in terms of skeleton branches. Several statistical measures are used to characterise the triangulation branches. The measures enable selective generalisation of different types of line feature, leading to the possibility of user-specification of the style of generalisation. In our implementation of the approach, the triangulation is updated dynamically to allow both sides of multiple lines to be processed, while guaranteeing topological consistency between the resulting generalised lines.
32895841
Software Change Management
Software projects change rapidly, which makes efficient change management a major challenge for the software industry. This challenge was poorly met for years because of rudimentary tools. The paper considers how modern change management, or configuration control tools must encompass changes affecting every kind of software deliverable and artifact.
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
33896540
A Triangulated Spatial Model for Cartographic Generalisation of Areal Objects
Cartographic generalisation involves interaction between individual operators concerned with processes such as object elimination, detail reductions amalgamation, typification and displacement. Effective automation of these processes requires a means of maintaining knowledge of the spatial relationships between map objects in order to ensure that constraints of topology and of proximity are obeyed in the course of the individual generalisation transformations. Triangulated spatial models, based on the constrained Delaunay triangulation, have proven to be of particular value in representing the proximal and topological relations between map objects and hence in performing many of the essential tasks of fully automated cartographic generalisation. These include the identification of nearby objects; determination of the structure of space between nearby objects; execution of boundary simplification, merge and collapse operations; and the detection and resolution, by displacement, of topological inconsistencies arising from individual operators. In this paper we focus on the use of a triangulated model for operations specific to execution of merge operations between areal objects. The model is exploited to identify the regions of space between nearby objects and to execute merge operations in which the triangulation is used variously to adopt intervening space and to move adjacent rectangular objects to touch each other. Methods for updating the triangulation are described.