<nested-kwd> Nested Keyword
Hierarchical or nested keyword, in which several levels of a taxonomy that pertains to the standard can be described.
Language in Keywords
Keywords are contained in <kwd-group> elements. There may be several <kwd-group>s, each of which can be identified separately by language, vocabulary, or taxonomy source. Since different languages could mean, for example, different writing directions, none of the individual keyword elements (<kwd>, <compound-kwd>, <nested-kwd>) take the @xml:lang attribute; that is reserved for the <kwd-group> element. This means that if there are keywords in several languages they should be in different <kwd-group>s.
For controlled vocabularies, two attributes can be used to link a keyword to specific term source in a controlled vocabulary:
- @vocab-term — This attribute holds the canonical form of the keyword as expressed in the vocabulary named in the <kwd-group>. The content of the keyword element (<kwd>, <compound-kwd>, <nested-kwd>) need not be exactly the same as the canonical form of the term, as the keyword element content might be a user-specific variant, for example, the term in another language.
- @vocab-term-identifier — This attribute holds a unique identifier and possible pointer to the specific term in the named vocabulary (typically a URI or DOI reference), but @vocab-term-identifier could be an item number or other system-specific identifier.
If the controlled vocabulary is it not named on the <kwd-group>, it is also possible to use two additional vocabulary attributes on <nested-kwd> to name the entire controlled vocabulary:
- @vocab — This attribute holds the name of a controlled or generic (uncontrolled) vocabulary, taxonomy, ontology, database, thesaurus, etc. that is the source of the keywords in the group, for example, “CRediT”, “inspec”, “structural engineering”, or “VWL”. In cases where there is no named vocabulary, the @vocab attribute should be set to “uncontrolled”.
- @vocab-identifier — This attribute holds a unique identifier and possible pointer to the named vocabulary (typically a URI or DOI reference).
Models and Context
<!ELEMENT nested-kwd %nested-kwd-model; >
Expanded Content Model
((kwd | compound-kwd)+, nested-kwd*)
3-level nested list
... <kwd-group kwd-group-type="xyw-food-taxonomy"> <nested-kwd> <kwd>beverages</kwd> <nested-kwd> <kwd>alcoholic</kwd> <nested-kwd> <kwd>beer</kwd> <kwd>martini</kwd> <kwd>wine</kwd> </nested-kwd> </nested-kwd> <nested-kwd> <kwd>dairy</kwd> <nested-kwd> <kwd>milk</kwd> <kwd>drinkable yogurt</kwd> <kwd>milkshakes</kwd> </nested-kwd> </nested-kwd> </nested-kwd> </kwd-group> ...