A tree for rocks—hierarchies in stratigraphic databases

Abstract

In this paper we present a new data model for a computer-supported management of stratigraphic information in relational databases, with special consideration to the hierarchical order of stratigraphic units. The huge amount of data on stratigraphic units provided by earth scientists during the last decades requires data models which—besides names, ages and background information such as used taxa in biostratigraphic units—can store both the position of a single unit within a stratigraphic column as well as its position within the stratigraphic hierarchy. The hierarchy management in the present data model is based on a modification of the nested-set data model, which is the core of the stratigraphy.net stratigraphic database system ( http://www.stratigraphy.net). The nested-set data model allows one to store alternative classifications of stratigraphic units with theoretically unlimited number of tree levels and unlimited amount of tree elements. Multiple hierarchies based on different disciplines such as biostratigraphy or lithostratigraphy can be stored in databases using the model presented here. In comparison to other models, the modified nested-set data model allows a high query performance. It permits an almost unlimited flexibility in describing the complex nature of stratigraphical information without limitations in the definition of standard query language queries. The application of this model is presented with detailed examples from the stratigraphy.net database.