Defining a water quality vocabulary using QUDT and ChEBI

Abstract

Vocabularies of observed properties and associated units of measure are fundamental to understanding of groundwater, surface water and marine water quality observations. The ability to support annotation of observation values from the disparate data sources with appropriate and accurate metadata is crucial to achieving interoperability; that is, precisely describing metadata relating to the magnitude of a physical quantity denoted by a unit of measure in a machine readable format. Previous projects have developed stand-alone water quality vocabularies, which provide limited support for cross-system comparisons or data fusion. We propose that relationships between the water quality concepts, the associated chemical entities and appropriate units of measure be represented formally using ontologies. As part of the development of a new water quality ontology for groundwater and marine domains, we have reused and aligned our definitions with existing ontologies. We use the 'Quantities, Units, Dimensions, Data Types' (QUDT) ontology to provide a consistent model of measurable quantities and units, and the Chemical Entities of Biological Interest (ChEBI) ontology for observations relating to chemical concentrations. In this paper we demonstrate reuse of these ontologies for describing observation values in the water quality domain. We show how QUDT can be used to define additional quantity kinds and units of measure relevant for the domain and how use of ChEBI enriches the water quality ontology, while maintaining separate ontology governance.