Study On Formal Representation Of Geographic Ontology And Its Application In Map Services

Ontology, originally a philosophical concept, it has gained more and more attention among researchers in the field of computer science recently, and it becomes more and more important as it is applied to different fields such as knowledge engineering, database design, information modeling, information query and so on.Ontology is not only given more attention in the field of computer science, but also in GIS. The importance of geographic ontology has been recognized from the last 90's. At present, many foreign experts and research institutes are engaged in researching geographical ontology and do some groping work. But few experts refer to this problem at home.Ontology is very significant in the fields such as concept model of spatial information, sharing and interoperation of spatial information, and research of geographic category. Its most important significance is to enrich the semantic theory of spatial information, which is proved by applying it to the filed of knowledge engineering. The research of ontology will become the important method to understand the geographic information and GIS intensively.Geographic ontology is a very complex and intricate concept. As a philosophical concept, ontology has the most ambiguous meanings, and it is first introduced into information science, then into the field of GIS. When many experts begin to research geographical ontology, they just transplant ontology concept of information science into GIS, not consider the particularity of geographic information itself.In the paper, firstly the concept of geographic ontology is explained. Then the formal representation of geographic ontology and application in map services is illustrated in detail. The main research work is divided into parts as follows:1. The concept of geographic ontology is researched by tracing back to the origin of ontology concept, and the meaning of ontology in philosophy and information science is reviewed. And it tries to build the basic theory system of geographic ontology, which helps to understand the researching field, meaning and development direction of geographic ontology. The three meanings of geographic ontology are put forward: philosophy ontology, information ontology and spatial ontology. Philosophy ontology mainly refers to studying geographic objects, concepts, categories, relations,processes. Spatio-temporal ontology, ontology of vagueness and ontology of scale are also the research ranges of philosophy ontology. Information ontology mainly refers to the formal specification of sharing geographic concepts, which applies to the sharing and interoperation of geographic information, integration and services of geographic information and so on. Spatial ontology is different from general information ontology because geographic ontology has not only common attribute character, but also important spatial character.2. Based on analyzing the present logical structure of ontology and geographic ontology, macro-structure and micro-structure of geographic ontology are presented. The former is a triple structure, namely O_macro = < Class, Property, Individuals The latter is a septuple structure, namely Omicro = < C, R, H, P, P , P , I>. On the basis of summing up the present methods of building geographic ontology, this paper concludes that the exsiting methods can be utilized synthetically to construct geographic ontology. The most difficult to build geographic ontology is not how to choose the appropriate method, but how to determine the geographic concepts, the relations among concepts, especially the properties of concepts. Ontological strata, a concept brought forward by Guarino, can be used to guide the process of building geographic ontology.3. The paper introduces some ontology representation languages and concludes by suggesting OWL as the appropriate language for building geographic ontology. OWL is researched emphatically. The inner structure and advantages of OWL are discussed and analyzed. And some examples are designed to prove the advantages of OWL. By comparing OWL and GML, the author finds that GML can only solve the heterogeneity of syntax, not the heterogeneity of semantic, but OWL can represent the abundant semantic information.4. Geographic ontology is quite distinct from the general information ontology in that it should represent spatial properties as well as attribute properties. Unfortunately, the existent ontology representation languages cannot describe spatial properties and spatial relations of geographic ontology because they are mainly for representing the general information ontology. This paper proposes to construct some formal axioms about spatial properties and spatial relations with the help of three theoretical tools, which are mereology, location theory and topology. And then add these new axioms to the OWL axioms to build geographic ontology which can represent its spatial properties. The tests prove that the formal representation mechanism is feasible andcan describe spatial properties of geographic ontology effectively.5. The theoretic research of geographic ontology is hot;but it is seldom practically used. The application of geographic ontology is still a very feeble step. Therefore;how to use ontology to describe and improve the service quality of map is discussed finally. For the users;the map is the efficient method of representing spatial information. But during the geographic information services;agents need be used to find and match all kinds of service. In the traditional map;the information is understood by the people;not by the agents. Therefore geographic ontology encodes the semantic information that people obtain from the map in a machine-readable manner. Second;present GIS lacks for the deduced competence;but geographic ontology can enhance the deduced competence because it has abundant semantic information.