A Data Model for Exploration of Temporal Virtual Reality Geographic Information Systems

Geographic information systems deal with the exploration, analysis, and presentation of geo-referenced data. Virtual reality is a type of human-computer interface that comes close to the way people perceive information in the real world. Thus, virtual reality environments become the natural paradigm for extending and enhancing the presentational and exploratory capability of GIs applications in both the spatial and temporal domains. The main motivation of this thesis is the lack of a framework that properly supports the exploration of geographic information in a multi-dimensional and multi-sensorial environment (i.e., temporal virtual reality geographic information systems). This thesis introduces a model for virtual exploration of animations. Virtual exploration of animations is a framework composed of abstract data types and a user interface that allow non-expert users to control, manipulate, analyze, and present objects\u27 behaviors in a virtual-reality environment. In the model for virtual exploration of animations, the manipulation of the dynamic environment is accomplished through a set of operations performed over abstractions that represent temporal characteristics of actions. An important feature of the model is that the temporal information is treated as first-class entities and not as a mere attribute of action\u27s representations. Therefore, entities of the temporal model have their own built-in functionality and are able to represent complex temporal structures. In an environment designed for the manipulation of the temporal characteristics of actions, the knowledge of relationships among objects\u27 behaviors plays a significant role in the model. This information comes from the knowledge base of the application domain and is represented in the model through constraints among entities of the temporal model. Such constraints vary from simply relating the end points of two intervals to a complex mechanism that takes into account all relations between sequences of intervals of cyclic behaviors. The fact that the exploration of the information takes place in a virtual reality environment imposes new requirements on the animation model. This thesis introduces a new classification of objects in a VR environment and describes the associated semantics of each element in the taxonomy. These semantics are used to direct the way an object interacts with an observer and with other objects in the environment

RADGIS - an improved architecture for runtime-extensible, distributed GIS applications

A number of GIS architectures and technologies have emerged recently to facilitate the visualisation and processing of geospatial data over the Web. The work presented in this dissertation builds on these efforts and undertakes to overcome some of the major problems with traditional GIS client architectures, including application bloat, lack of customisability, and lack of interoperability between GIS products. In this dissertation we describe how a new client-side GIS architecture was developed and implemented as a proof-of-concept application called RADGIS, which is based on open standards and emerging distributed component-based software paradigms. RADGIS reflects the current trend in development focus from Web browser-based applications to customised clients, based on open standards, that make use of distributed Web services. While much attention has been paid to exposing data on the Web, there is growing momentum towards providing “value-added” services. A good example of this is the tremendous industry interest in the provision of location-based services, which has been discussed as a special use-case of our RADGIS architecture. Thus, in the near future client applications will not simply be used to access data transparently, but will also become facilitators for the location-transparent invocation of local and remote services. This flexible architecture will ensure that data can be stored and processed independently of the location of the client that wishes to view or interact with it. Our RADGIS application enables content developers and end-users to create and/or customise GIS applications dynamically at runtime through the incorporation of GIS services. This ensures that the client application has the flexibility to withstand changing levels of expertise or user requirements. These GIS services are implemented as components that execute locally on the client machine, or as remote CORBA Objects or EJBs. Assembly and deployment of these components is achieved using a specialised XML descriptor. This XML descriptor is written using a markup language that we developed specifically for this purpose, called DGCML, which contains deployment information, as well as a GUI specification and links to an XML-based help system that can be merged with the RADGIS client application’s existing help system. Thus, no additional requirements are imposed on object developers by the RADGIS architecture, i.e. there is no need to rewrite existing objects since DGCML acts as a runtime-customisable wrapper, allowing existing objects to be utilised by RADGIS. While the focus of this thesis has been on overcoming the above-mentioned problems with traditional GIS applications, the work described here can also be applied in a much broader context, especially in the development of highly customisable client applications that are able to integrate Web services at runtime