THE ROLE OF CONCEPTUAL MODELS IN GEOINFORMATICS

Computer information systems that will archive, query, retrieve, and display geologic information tailored to specific requirements are the foundation for a leap in scientific development similar to that fostered by the invention of the geologic map. In order to achieve this potential, some standardization of a conceptual model for basic elements of geoscience is required to provide a consistent framework for developing interoperable systems using a semantic markup language as an interchange format. These models must be developed in the framework of larger community modeling efforts for interdisciplinary knowledge domains, such as time, location, material science, and physics.

Models are presented for concepts that are central to geologic science: Earth material, geologic units, geologic structure, and geologic time scales. The described models build on the NADM C1 model [North American Geologic-Map Data Model Steering Committee, 2004], and are being implemented for the USGS National Geologic Map Database Project. An Earth material is a substance defined by chemical constituents, in concert with crystal structure, physical properties, or properties related to the nature and arrangement of constituent particles. Earth material is a mass noun, not countable. A geologic unit is a part of the Earth located and distinguished from other parts of the Earth based on geologic properties. Geologic units are countable. A geologic structure is a configuration of Earth material within the Earth, and may or may not be countable. The existence of a geologic structure requires the existence of some Earth material substrate. Geologic time scales are modeled as hierarchical collection of named intervals within a temporal topologic complex (ISO 19108) constrained such that only one path between nodes in the complex may be subdivided. A top-level vocabulary defines subclasses of these concepts, and description schemas specify relationships and attributes used to characterize defined classes and instances that extend the top-level subclasses. A geologic map is modeled as a particular instance of a more general geoscience knowledge representation framework. Models are presented as UML static class diagrams.