Wrapper element for multi-part keywords (for example, a code and its description/title/meaning).
When to Use Compound Keyword: Some keywords are a simple word or phrase; such keywords should generally be tagged using the <kwd> element. The <compound-kwd> element is used when keywords are composed of multiple parts, such as:
- a code and its meaning, or
- an abbreviation and its expansion
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.
Vocabulary Attributes: For controlled vocabularies, two attributes can be used to link a keyword to its term source:
- @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>) might not be exactly the same as the canonical form, 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.
INSPEC keywords added by an SDO:
... <kwd-group id="KG1" originator="ASME" vocab="Inspec" vocab-identifier="http://www.theiet.org/resources/inspec/about/records/ithesaurus.cfm" xml:lang="en"> <compound-kwd id="KG1.1"> <compound-kwd-part content-type="code">A7865P</compound-kwd-part> <compound-kwd-part content-type="text">Optical properties of other inorganic semiconductors and insulators (thin films/low dimensional structures)</compound-kwd-part> </compound-kwd> <compound-kwd id="KG1.2"> <compound-kwd-part content-type="code">A7865T</compound-kwd-part> <compound-kwd-part content-type="text">Optical properties of organic compounds and polymers (thin films/low dimensional structures)</compound-kwd-part> </compound-kwd> </kwd-group> ...