Synset
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In metadata, a synonym ring or synset, is a group of data elements that are considered semantically equivalent for the purposes of information retrieval.{{Citation needed|reason=It is easy to find definitions of "synonym ring" as a set of terms that are synonymous, but finding a definition in terms of "data element" seems hard. Thus, citation needed.|date=December 2022}} These data elements are frequently found in different metadata registries. Although a group of terms can be considered equivalent, metadata registries store the synonyms at a central location called the preferred data element.
According to WordNet, a synset or synonym set is defined as a set of one or more synonyms that are interchangeable in some context without changing the truth value of the proposition in which they are embedded.
Example
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The following are considered semantically equivalent and form a synonym ring:
foaf:person
gjxdm:Person
niem:Person
sumo:Human
cyc:Person
umbel:Person
Note that each data element has two components:
- Namespace prefix, which is a shorthand for the name of the metadata registry
- Data element name, which is the name of the object in each of the distinct metadata registry
Expressing a synonym ring
A synonym ring can be expressed by a series of statements in the Web Ontology Language (OWL) using the classEquivalence or the propertyEquivalence or instance equivalence statement – the sameAs property.