Facets and measures of gene ontology annotation quality in model organism databases

Model organism databases are important repositories of data and information for biomedical research, but are useful to scientists only if the information they contain meets certain levels of quality. This methodology paper describes six facets of information quality applicable to Gene Ontology (GO) annotations in model organism databases, and defines corresponding metrics to be used in measuring the quality of annotations made by one or more human database curators. The defined facets and measures of annotation quality are: consistency, reliability, specificity, completeness, accuracy, and validity. Contextual factors, and factors affecting internal and external validity, are also discussed.