A controlled vocabulary gives each concept one preferred term; others point to it

What it is

A controlled vocabulary locks one preferred term per concept and registers every other wording as a non-preferred term that points at it. Display, cataloguing, and default retrieval use the preferred term. Non-preferred terms are entrances, not another concept. This is the vocabulary form of “one label per concept”: it specifies that a concept node may have only one public name, and how aliases hang off that node, rather than unifying copy ad hoc.

A list of near-synonyms with no pointing relation is not a controlled vocabulary. It is a list that will split again.

Why it happens

Once a concept has two official names, cataloguing and lookup each pick one, and the collection splits in the index. The preferred term locks the write side: new objects may only take that word. Non-preferred terms open the read side: an alias the user brings is folded onto the same node, not refused or minted as a new class. Pointing is one-way; the node’s identity does not grow as aliases are added.

The “control” is admission: which string may be preferred, which may only be an entrance, has to be ruled on. Without a ruling, a newly coined marketing name becomes a second preferred term and the vocabulary exists in name only.

Studying it

Check whether a concept has exactly one writable name, and whether aliases actually point at it.

• Paradigms: sample core concepts, list every writable label on cataloguing UIs, and see whether more than one preferred term exists; retrieve with a non-preferred term and see whether it lands on the same node. Contrast with vocabularies that offer near-synonyms as parallel options.
• Independent variables: enforcement of a single preferred term, whether non-preferred terms can be written onto objects or only queried, whether pointing is one-way.
• Dependent variables: label split count under one concept, overlap of alias retrieval with preferred-term retrieval, whether a new marketing word bypassed the vocabulary as a new preferred term.
• Methodological note: a UI may show one dropdown while the store still holds historical aliases as official values. Pair against object records, not only the current form. Experts agreeing that “it means the same” is not the same as records already pointing at one node.

Where it stops holding

Multiple languages are not multiple preferred terms; each language has one preferred term, and the cross-language relation is translation. When law requires a statutory name and a common name on display, the statutory name may be a second display string; the write side should still have one concept id and one preferred term, or cataloguing will mint a node per statutory name. Unstable new concepts can sit as candidates without becoming preferred yet; locking a still-contested word forces a mass retag later.

Applying it

• On each concept node record: preferred term, non-preferred list, who may change the preferred term. Cataloguing controls may only attach the preferred term.
• Non-preferred terms appear in search, synonyms, and import cleaning—not as choosable options in nav and filters.
• When a second writable name appears, demote it to non-preferred and migrate data. Do not “keep both and pick at display time.”
• Verify by tagging the same object once with the preferred term and once with a non-preferred term; the store should hold one preferred value. Two records or two writable values means the vocabulary is not controlling the write side.

Related

• Within the group: G1.10.2 A thesaurus describes hierarchy and association with broader, narrower, and related terms · G1.10.3 Authority files hold canonical names for entities and resolve homographs and aliases · G1.10.4 Controlled vocabularies are staff-maintained, unlike folksonomies · G1.10.5 At retrieval, non-preferred terms map to the preferred term and yield the same results · G1.10.6 Vocabularies need versioning and change records as the domain evolves
• Adjacent: G1.04 Labeling systems · G1.08 Terminology consistency · T1.04 Terminology consistency and glossaries
• Search terms: controlled vocabulary · preferred term · non-preferred term