This paper introduces a geographic information system architecture based on ontologies. Ontology plays a central role in the definition of all aspects and components of an information system in the so-called ontology-driven information systems. The system presented here uses a container of interoperable geographic objects. The objects are extracted from multiple independent data sources and are derived from a strongly typed mapping of classes from multiple ontologies. This approach provides a great level of interoperability and allows partial integration of information when completeness is impossible.

. Categorical coverages are popular for the presentation of thematic data in cartographic form and have gained widespread use. Routines for their preparation are included in most GIS software. Categorical coverages are simple to implement and easy to understand. The popularity of the categorical coverage is closely related to the intuitive rules that determine its behavior. This paper presents a formalization of these rules based on the concepts of a partition of space and the refinement of such partitions of space. A family of categorical coverages is defined as all categorical coverages that can be produced from a data set through aggregations of categories. It is shown that categorical coverages are partially ordered by 'refinement'of partitions. This ordering is preserved in the mapping from the ordering of the partition of the attribute domain to the partition of space. This formalization is not only useful for implementors of GIS, but the list of possible operations and their pro...

Geographic Information Systems manage data with respect to spatial location and that data is presented graphically as a map or sketch. A database of objects with some geometric properties is used to render these objects graphically for different tasks. Typically these tasks require graphical presentations at different levels of detail, ranging from overview screens to detailed views [Herot et al., 1980]. Practically a base map is stored and its scale changed graphically. Without major distortions, only changes to twice or half the original scale are feasible by simple numeric scale change. A function to draw cartographic sketches quickly and in arbitrary scales is needed. We propose a multi-scale hierarchical structure where renderings of spatial objects with increasing detail are stored: a directed acyclic graph (DAG). These are used to compose a topographic map at a particular scale. We assume that the object renderings for the DAG already exist. Methods to select objects for rendering are based on the importance of the object for a particular taskand on the principle of equal information density. We propose a method for determining information density, namely measuring the ink content of the map.

In this paper, we develop a model for the structure of multi-scale data derived from a map series. First we present a model of a map. We give an ontology of map elements and assign them to the objects of the model.. Then we derive a model for a series of maps, connecting several of the map models with the help of tree structures. This model is called the map cube model, the horizontal axes denoting 2D space and the vertical axis denoting level of detail. A formal model of the map model and of the map cube model is given in Gofer.

GIS need a function to draw sketches quickly and in arbitrary scales. We propose a multiscale hierarchical spatial model for cartographic data. Objects are stored with increasing detail and can be used to compose a map at a particular scale. This results in a multi-scale cartographic forest when applied to cartographic mapping. The structure of the multi-scale forest is explained. It is based on a trade-off between storage and computation. Methods to select cartographic objects for rendering are based on the principle of equal information density. 1. INTRODUCTION Geographic Information Systems manage data with respect to spatial location and those data are presented graphically as a map or sketch. There are a number of similar graphics applications, where a database of entities with some geometric properties is used to render these entities graphically for different tasks. Typically these tasks require graphical representations at different levels of detail, ranging from overview scree...

The size and complexity of modern geographic datasets continue to grow and with that growth comes an increased difficulty in assessing the usefulness of a particular dataset for a particular problem. The task of browsing through a large database is rapidly becoming impractical because of the shear volume of the data, therefore, the information potential of the database is lost because the scope of the database is beyond comprehension. This editorial promotes new methodologies beyond the use of descriptive metadata to support a users desire to find a dataset suitable for his or her analysis.

The integration of information of different kinds, such as spatial and alphanumeric information, at different levels of detail is a challenge. While a solution is not reached, it is widely recognized that the need to integrate information is so pressing that it does not matter if detail is lost, as long as integration is achieved. This paper shows the potential for extraction of different levels of information inside the framework of ontology-driven geographic information systems.