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.

The integration of information of different kinds, such as spatial and alphanumeric 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 information retrieval at different levels of granularity inside the framework of information systems based on ontologies. Ontologies are theories that use a specific vocabulary to describe entities, classes, properties and functions related to a certain view of the world. The use of an ontology, translated into an active information system component, leads to Ontology-Driven Information Systems and, in the specific case of GIS, leads to what we call Ontology-Driven Geographic Information Systems.

Over the last ten years, a subfield of GIScience has been recognized that addresses the linkage between human thought regarding geographic space and the mechanisms of implementing these in computational models. This research area has developed an identity through a series of successful international conferences and the establishment of a journal. It has also been complemented through community activities such as international standardization efforts and GIS interoperability. Historically, much of the advancement in computational methods has occurred at---or close to---the implementation level, as exemplified by the attention on the development of spatial access methods. Significant progress has been made at the levels of spatial data models and spatial query languages, although we note the lack of a comprehensive theoretical framework comparable to the relational data model in databases management systems. The difficult problems that need future research efforts are at the highly abstract level of capturing semantics of geographic information. A cognitive motivation is most promising as it shapes the focus on the users' needs and points of view, rather than on efficiency as in the case of a bottom-up system design. We also identify the need for new research in fields, models of qualitative spatial information, temporal aspects, knowledge discovery, and the integration of GIS with database management systems.

Data and knowledge exchange among users of urban information systems presents many challenges. This paper discusses issues related to the use of ontologies in the development of urban geographic information systems and proposes the creation of software components from diverse ontologies as a way to share knowledge and data. These software components are derived from ontologies using an object-oriented mapping. The translation of an ontology into an active information system component leads to ontology-driven information systems and, in the specific case of geographic applications, to ontologydriven geographic information systems. We analyze the urban environment from the ontologists' point of view and make some inferences about the relationship between knowledge and data sharing, and the theory of bona fide and fiat objects. We also discuss implementation issues, such as the use of Ontolingua as an ontology editor, and CORBA IDL generator, CORBA, and Java as object platforms.

Guarino for their prompt responses to my questions. Third, to all my colleagues and friends in the Department of Spatial Information Science I would like to thank you for sharing the good and bad moments of my study life. I feel fortunate for having being part of a friendly environment that made my Ph.D. program an enjoyable and unforgettable experience. iii Fourth, I thank the support and funding from the University of Concepcin, Chile, and the initial funding from the Fulbright foundation. Further funding from the National Center of Geographic Information and Analysis, the National Imagery and Mapping Agency, and Lockheed Martin are gratefully acknowledged. Most important, I thank the continuous support, love, and patience of Christian and Alicia. This long journey would not have been possible without them. iv Table of Contents Acknowledgments .......................................................................................................ii List of Figu

Incorporating abstraction methods, such as aggregation and association, into information system design methodologies has improved our ability to model the real world. The semantically-higher level objects that result from these abstractions are referred to as composite objects. These objects play an important role in spatio-temporal knowledge representation and query formulation, although little has been done so far on formalizing operations involving these types of objects. In this investigation, the semantics associated with composite objects are explored as is the role of object identity for composite objects. Object identity refers to that trait which distinguishes an object from all others. The different semantics associated with creating composite objects and adding parts to composites are discussed and a set of basic identity-based change operations for composites, including separation and elimination operations, are described. Formalizing the operations relating to composite objects aids in improving current spatial data models and leads to advances in spatial-temporal query languages.

The human-computer interface is a crucial element in the design of the next generation of Geographic Information Systems (GISs). We discuss the user interface design process by separating the formalization of the problem domain (identifying the objects a user manipulates, and their pertinent operations) from its visualization (describing human-computer interaction techniques such as windows and dialog boxes). This framework is used to examine the process of manipulating attribute data in a GIS on the basis of the common cartographic concept of a categorical coverage. The characteristics of categorical coverage data and the user requirements for interacting with this data are formalized in the form of a set of fundamental objects and operations. A visualization for a windows-icons-menus-pointing devices (WIMP) interface is presented.

Introduction The large majority of current systems for handling geospatial information are static, concentrating on a single temporal snapshot, usually the current state. Changes in the application domain are tracked in the system by performing updates and erasing information on the past. In recent years there has evolved a body of research, both in the general database community (Snodgrass 1992) and in the spatial database community (Al Taha et al 1993) for adding temporal dimensions. That research addresses the issue of `time in the system', where the challenge is to provide computational models that enable past, current and future states of the application domain (valid time) and the system (transaction time) to be handled in the temporal database. Work presented in this chapter, however, is concerned with a different aspect of temporal systems, referred to as `the system in time', where we are concerned to handle in a dynamic system a model of the r

This research addresses the problem of obtaining useful knowledge from multiple theme geographic data where the size and complexity of the dataset challenges human compre-hension. A theoretical foundation for geographic knowledge discovery in databases is de-veloped commencing with Pawlak’s (1982, 1991) theory of abstract knowledge. Pawlak’s theory is founded on notions of equivalence relations and classification. These ideas are combined with the well-known mathematical concepts of set definition by extension and by intension to develop the concepts of extensional knowledge (i.e facts) and intensional knowledge (e.g. rules). The theory traverses the concepts of generalisation, specialisation, induction, deduction, unsupervised learning and supervised learning. Further considera-tions lead to proposing that empirical objects are dependent upon, and a consequence of, an intelligent agent’s sensory experience of real-world phenomena. The a priori existence of objects in nature is rejected. A theory of empirical spatial knowledge is developed, based on the idea that spatial experience of reality is fundamentally dependent upon the spatial configuration of the sensors of the sensing entity. It is shown that the spatial relationships

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.