| In the past, for various reasons, GIS software has not been able to represent many of the complexities of the world and human perceptions of it. Along with concepts such as the temporal change, three-dimensionality, and uncertainty inherent in reality and cognition, gradation plays an important role in how the world works. This dissertation pulls together previous work concerning geographical entities with gradual boundaries into a single framework and vocabulary.; Once a degree of understanding is obtained concerning the variety of causes and forms of gradation, the representation of this phenomenon in GIS is investigated. Several possible data models and structures are described, including some introduced elsewhere and some developed by the author, and an evaluation of the effectiveness of each in dealing with a particular application.; Through this research, it is found that the variety of characteristics found in gradation situations leads to a variety of relevant solutions. Several of the proposed structures appear to be practical to implement in current software, while others would require a total redesign of GIS. |
