PROGRESS REPORT ON THE IMPLEMENTATION OF A PROTOTYPE NATIONAL GEOLOGIC MAP DATABASE

The National Geologic Mapping Act of 1992 and its Reauthorizations contain provisions that mandate the establishment of a National Geologic Map Database (NGMDB), distributed through links to Federal and State holdings, to include geologic maps and related geoscience data developed under the auspices of the Mapping Act. Development of the NGMDB emphasizes the database as an archive of geoscience information from which geologic maps are a type of report. The NGMDB database implementation is designed for depth of knowledge representation and flexibility, not for simplicity or performance. It includes provisions to record alternative interpretations, evolving terminology and science paradigm, uncertainty, incomplete knowledge, and metadata pertaining to data acquisition, processing, and automation. The objective is integration of geologic data from published maps by different authors at different scales, as well as newly acquired field data. NGMDB implementation of the NADM C1 conceptual model revolves around three logical elements-Vocabularies, Description Schema, and Description Instance. Vocabularies are collections of terms and text definitions that enumerate things thought to exist in a domain or possible values for properties. A Vocabulary may include relationships between the represented concepts (terms), in particular a 'kind of' hierarchy where appropriate. The Description Schema is an explicit representation of the data model implemented by a dataset; analogous to an XML or OWL schema, and is included as part of the data. It specifies kinds of data objects and their properties, relationships between objects, and rules that determine valid database conditions. Description instances are collections of related database records conforming to the Description Schema, which together specify attribute values for some entity of interest. Feature level metadata may be attached to any data instance. The database prototype includes data for the northwest part of the Phoenix, AZ, metropolitan area, and is implemented using standard relational (SQL) database technology (currently MS Access and Microsoft SQL Server) integrated into a geographic information system as an ESRI Geodatabase that links 'thematic' information with geologic map visualization. A data entry tool is under development.