A formal model for the geologic time scale and global stratotype section and point, compatible with geospatial information transfer standards

The geologic time scale is a complex data structure composed of abstract elements that represent time intervals and instants and their relationships with specific concrete representations in the geologic record as well as the observations made of those concrete representations. The International Union of Geological Sciences' International Commission on Stratigraphy guidelines recommends a very precise usage of the relationships between these components in order to establish a standard time scale for use in global correlations. However, this has been primarily described in text. Here, we present a formal representation of the model using the Unified Modeling Language (UML). The model builds on existing components from standardization of geospatial information systems. The use of a formal notation enforces precise definition of the relationships between the components. The UML platform also supports a direct mapping to an eXtensible Markup Language (XML)-based file format, which may be used for the exchange of stratigraphic information using Web-service interfaces.