Rat Strain Ontology (RSO) annotations were automatically assigned to RGD rat strain records on the basis of pre-existing associations between RSO terms and rat strain RGD IDs. These associations, via the assignment of a strain RGD ID as a synonym for the RSO term, were made during the process of RSO development by RGD curators. The RSO term was matched to the rat strain record by the strain RGD ID and the annotation was made using the evidence code IEA, "Inferred from Electronic Annotation".