A Survey of Identifiers and Labels in OWL Ontologies

We present a survey of the usage and style of identifiers and labels of named entities in a corpus of OWL ontologies. We investigated the frequency of use of both labels and meaningful or meaningless identifiers in those ontologies. We also surveyed common practices of lexical encoding styles for identifiers. We found that most ontologies do not use labels for named entities. When they do use labels, those labels are mostly meaningful and most ontologies also used meaningful identifiers. CamelCase style appears to be the most widely used style of lexical encoding for identifiers. We observed, however, that the majority of the ontologies use a mixture of two or more lexical encoding styles. The result of this survey is useful when considering strategies, for example, natural language generation from ontologies or converting artefacts, such as OWL ontologies, into languages like the Simple Knowledge Representation System (SKOS), where the notion of label is important. Given that labels are optional in OWL ontologies, what is the best way to handle the label selection when converting them into SKOS? Merging multiple entities may require selection from labels or identifiers assigned to these entities for skos:prefLabel and skos:altLabel.