Temporal Ontologies for Geoscience: Alignment Challenges

Abstract:

Time is a central concept in geoscience. Geologic histories are composed of sequences of geologic processes and events. Calibration of their timing ties a local history into a broader context, and enables correlation of events between locations. The geologic timescale is standardized in the International Chronostratigraphic Chart, which specifies interval names, and calibrations for the ages of the interval boundaries.

Time is also a key concept in the world at large. A number of general purpose temporal ontologies have been developed, both stand-alone and as parts of general purpose or upper ontologies. A temporal ontology for geoscience should apply or extend a suitable general purpose temporal ontology.

However, geologic time presents two challenges:

1. Geology involves greater spans of time than in other temporal ontologies, inconsistent with the year-month-day/hour-minute-second formalization that is a basic assumption of most general purpose temporal schemes;
2. The geologic timescale is a temporal topology. Its calibration in terms of an absolute (numeric) scale is a scientific issue in its own right supporting a significant community. In contrast, the general purpose temporal ontologies are premised on exact numeric values for temporal position, and do not allow for temporal topology as a primary structure.

We have developed an ontology for the geologic timescale to account for these concerns. It uses the ISO 19108 distinctions between different types of temporal reference system, also linking to an explicit temporal topology model. Stratotypes used in the calibration process are modelled as sampling-features following the ISO 19156 Observations and Measurements model.

A joint OGC-W3C harmonization project is underway, with standardization of the W3C OWL-Time ontology as one of its tasks. The insights gained from the geologic timescale ontology will assist in development of a general ontology capable of modelling a richer set of use-cases from geoscience.