Indian |
International | Geographic Information Infrastructure
The research on Metadata Management of Resource and Environment Spatial Database
2 The design of metadata standard The geography information metadata standards are continuously the research hot spots of international geography information society , and include that the United States organizations such as federation geography data committees ( FGDC ) , Europe geography information standardization committees ( CEN/ TC287 ) and international standard organization geography information committees ( ISO/TC211 ) etc all devote self to continuously the research of geography information metadata standards . At present, ISO/TC211 is as a result of near ten renewals of version, and has entered committee draft stage . Now our nation has also made a large number of efforts the standard aspect the research, has accomplished the nation geography information standard by the nation geography information foundation centers. Therefore nation resources and the environment database metadata standard is accomplished under international and premise that the national standard is soon issued. Thinking over completeness, accuracy, structure and the compatibility of standard, and has consulted and follow the newest many international standard , national standard or the functional standards with the international standard , for example,ISO/TC211 was at the final drafts put forward of 8 months Final Text Of CD 19115 Geographic Information - Metadata in 2001 , and the geography information center on nation foundation is at metadata put forward in 2001 standards geography information numeral product metadata on foundation . Moreover, the spatial data of RESD are to give first place to with space information (vector, reflection and raster, etc.) and with the attribute data are given first place to and possesses the space locating information, as well as the non- spatial data collection such as books document archives datum catalogue warehouses and law regulations data bases etc. According to the concrete requirement, we have worked out the standard that is suitable. 2.1 Structure design of metadata The standard includes seven kinds and three kinds public data. Seven kinds include : Identification, basic information about the data set; Data Quality, the overall of data quality information; Spatial Data Organization, the organization method of data set spatial information; Spatial Reference, the description of the reference frame of the coordinate of data set as well as coded system; Entity And Attribute , the details information about the data set; Distribution, the publishing and procure information; Metadata Reference, the metadata condition and the information of responsible department at present; Three kinds of public data packs are drawn together : Citation, the concise information when quoting and the reference data collection; Date, the information of date and the time of concerned incident is provided Contact, about individual or organization quoted in the major subset . Public data not single uses of sheet , the object quoted as other elements. The concerned standard that fits internationally and the nation is confined to the length , and is not given unnecessary details about at this the concrete content of concerned metadata again. Owing to the metadata complicated logical organization and relation are existed between various big kind , if the analysis is come to the method used towards the object ,it includes the inheritance relations such as ( single and multi ) , Composition, Aggregation and Association etc . The public data are as quoting the object , and are frequently quoted by other kind again . If only describing the metadata , will very hard express clearly with the two dimension table in common use . Therefore needing to show with the means of diagram.  Figure 1 The class MD_metadata’s definition and containment relationships with the other metadata classes The Unified Modeling Language is designed the graphic presentation method of structure as one kind towards the object , and is used by Object Management Group(OMG) and other organization as a standard . In the geography information series standard that ISO/ TC211 is working out includes the final draft put forward at present , and also all use UML generally as model language. Therefore we have used static structure figure in UML to express logical organization and the relation of each kind of metadata here. Class and attribute of class have been described with the data dictionary . Thus the complete metadata standard has been formed .This is also consistent with the international standard. The relation between class of metadata standard includes Generalization ( matches towards the object inheritance ) , Aggregation, Composition, Association etc. . In figure 1, MD_metadata is aggregated by MD_quality, MD_reference, MD_content and MD_spatialreference and follow system and MD_content expressions and MD_distribution, and this kind of relation is that association is got together to one kind of one-way . In the figure , the number represent multi . Such as is that 1..*, shows that the metadata has one or many identification to be known information between MD_metadata and the MD_identification . In addition , the important is still can realize the extension of metadata according to the new model element of the construction of UML Model Stereotypes above the model element of definition . |