Geographic Event Information Retrieval Based On Ontology

As been one of the main sources of information in magnitude natural disaster handling information service, geographic information plays an important part in disaster prevention and retrieval decision making. This makes geographic information retrieval service as a significant part in natural disaster information service system. While, the occurred natural disaster events request geographic event oriented geographic information retrieval service. That is, besides event description information, also getting related information automatically which is connected through geographic information with event. But traditional geographic information retrieval method can’t achieve it because of diversity in representation and fuzziness in description of geographic information, multiplicity in geographic information of disaster event, lack of connectivity between related information and event, and flaws in geographic information retrieval tool itself. Additionally, geographic data is organized by traditional method, and geographic information of different types is difficult to organize by event. The user must operate multi-source and heterogeneous system to get the related information with event. This makes traditional geographic information retrieval system not provide related information for event handling automatically. So it’s significant to research event oriented geographic information automatic retrieval. The paper uses ontology idea in researching geographic event oriented geographic information retrieval technology to fulfill the requirement of natural disaster information service. Ontology is applied widely in computer information science because of its good concepts hierarchy and capacity of maintaining semantic relation. It is mainly to resolve information semantic heterogeneity and query expansion problems in geographic information retrieval domain, thus capable to retrieve information in semantic layer. The paper constructs geographic event ontology to model geographic event and related information concepts, which utilizing the capacities of ontology maintaining semantic relation between geographic event and related information. Based on this work, the paper realizes event oriented geographic information retrieval mechanism.At first, the paper introduces the basic theory of ontology concept, construction, reasoning, and so on. Meanwhile, the functions of ontology in geographic information retrieval are discussed. Because of no reuse geographic event ontologies, the paper studies on ontology construction, and proposes a construction method of task centralized. That is using data as the task to be processed as constraint in constructing ontology, which makes the construction goal definite. Compared with the method of constructing ontology only from domain knowledge, the method can determine domain scope more quickly. Additionally, the UML model diagram is used to assist ontology construction. The method can decreases the difficulty of mapping ontology with database subsequently.Construction of geographic event ontology successfully provides the foundation for implementing event oriented geographic information retrieval, because it maintains the relation between geographic event and related information. But to realize retrieval combined with database, it must be connected to the concrete data. So the paper studies mapping natural disaster database to geographic event ontology, and propose the method of mapping between relational database and ontology based on data handling expression.Based on geographic event ontology, the paper proposes the implementation principle of geographic information retrieval based on ontology. It utilizes the advantage of semantic relations in ontology and ontology query language SPARQL, and its process is very simple. At the same time, a framework and process of geographic information retrieval are represented. Based on these works, a retrieval prototype system is implemented. Compared to traditional geographic information retrieval based on morphology of key words, this prototype system is based on ontology, and able to retrieve and matching information in semantic layer. It also has the capacity of retrieving information by event.In the end, the paper studies on the event oriented geographic information retrieval based on ontology query expansion through an experiment. By query expansion, the implicate information satisfied user query intention is retrieved, which improves the qualities of geographic information retrieval. Through the experiment, the rationality of geographic information retrieval mechanism based on ontology is validated, and the functions of ontology in geographic event oriented geographic information retrieval are concluded eventually.