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<kwd> Keyword

A keyword is a finding aid used to record one subject term, key phrase, abbreviation, indexing word, taxonomic structure, or other expression that is associated with a whole structure (such as an article). Keywords can be used for identification, searching, and indexing purposes. A keyword element (<kwd>) may contain a repetition of words found in the structure, or it may contain broader terms, narrower terms, related terms, or taxonomic identifiers used to find the structure in a search or provide semantic classification of the text by mapping a specific structure to a taxonomy.

Usage/Remarks

Keywords are contained in <kwd-group>s. A document may take multiple sets of keywords, with attributes such as @kwd-group-type, @specific-use, @xml:lang, or @vocab used to discriminate between the sets.
The <kwd> element may not take the @xml:lang attribute; that is reserved for the <kwd-group>. This means that keywords must be separated by language and placed into language groups.

Attribute Best Practice

If the content of the <kwd> element is a term from a controlled vocabulary (ontology, taxonomy, term-list, vocabulary, industry glossary, or other known source), the vocabulary identification attributes should be used to identify that source. The vocabulary term identification attributes may also be used, unless the vocabulary has already been named on the <kwd-group>.
Vocabulary Term Identification Attributes
Two attributes are used in this Tag Set to identify an individual term from a vocabulary (controlled or an uncontrolled):
vocab-term
The content of the element is the display version of the vocabulary or taxonomic term. The @vocab-term attribute holds the canonical version of the same term, as it appears in the vocabulary. For example, if the element display text content is “Digitized Version of Record” the attribute value might be “digitized-vor”
vocab-term-identifier
Unique identifier of the term within a specific vocabulary, such as (but not limited to) an item number, a URI, DOI, etc.
Vocabulary Identification Attributes
Two attributes are used in this Tag Set to identify a vocabulary. If these attributes have already been used on <kwd-group>, they need not be repeated on each <kwd>.
vocab
Name of the controlled or uncontrolled vocabulary, taxonomy, ontology, index, database, or similar that is the source of the term. For example, for a subject term, a value might be the IPC Codes (“ipc”) or MESH headings (“mesh”). For an uncontrolled term, the value might be an area of study such as “medical-devices” or merely the word “uncontrolled”.
vocab-identifier
Unique identifier of the vocabulary, such as (but not limited to) a URI or DOI. For example, for Dublin Core (DCC), the identifier may be “http://dublincore.org/documents/2012/06/14/dces/”.
Related Elements
This Tag Set contains several differently-structured types of keywords:
  • <kwd> is used with simple keywords: words or phrases.
  • <compound-kwd> is used with multi-part keywords, such as a keyword that is a code-and-term pair.
  • <nested-kwd> is used with hierarchical keywords structures, such as taxonomies, to record a portion of a taxonomic hierarchy. Both simple and compound keywords can be nested hierarchically.
  • <unstructured-kwd-group> is used to hold one long keyword string, which contains multiple constituent keywords that are not tagged individually.
Best Practice: In this Tag Set, nested keywords (<nested-kwd>) should be reserved for hierarchical material such as taxonomies. There are a few journal tag sets in which keyword nesting is used to simulate a two-part list. Such a keyword list should be tagged as a <def-list> instead.
Attributes
assigning-authority
content-type
vocab
vocab-identifier
vocab-term
vocab-term-identifier

Base Attributes

id
xml:base
Models and Context
May be contained in
<kwd-group>, <nested-kwd>
Description
Any combination of:
Content Model
<!ELEMENT  kwd          (#PCDATA %kwd-elements;)*                    >
Expanded Content Model

(#PCDATA | email | ext-link | uri | inline-supplementary-material | related-article | related-object | hr | bold | fixed-case | italic | monospace | overline | overline-start | overline-end | roman | sans-serif | sc | strike | underline | underline-start | underline-end | ruby | alternatives | inline-graphic | inline-media | private-char | chem-struct | inline-formula | tex-math | mml:math | abbrev | index-term | index-term-range-end | milestone-end | milestone-start | named-content | styled-content | fn | target | xref | sub | sup | x | break)*

Tagged Samples
Author’s keywords 
...
<article-meta>
 ...
 <abstract>...</abstract>
 <kwd-group kwd-group-type="author">
  <kwd>DNA analysis</kwd>
  <kwd>gene expression</kwd>
  <kwd>parallel cloning</kwd>
  <kwd>fluid microarray</kwd>
 </kwd-group>
</article-meta>
...
Multiple <kwd-group>s 
...
<article-meta>
 ...  
 <kwd-group kwd-group-type="Inspec">
  <kwd>diversity reception</kwd>
  <kwd>Doppler radar</kwd>
  <kwd>Doppler shift</kwd>
  <kwd>encoding</kwd>
  <kwd>optimisation</kwd>
  <kwd>orthogonal codes</kwd>
  <kwd>radar signal processing</kwd>
  <kwd>MIMO radar</kwd>
 </kwd-group>

 <kwd-group kwd-group-type="uncontrolled">
  <kwd>polyphase codes optimisation</kwd>
  <kwd>multiinput-multioutput radars</kwd>
  <kwd>radar performance</kwd>
  <kwd>diversity technique</kwd>
  <kwd>MIMO radar transmission</kwd>
  <kwd>diversity performance</kwd>
  <kwd>orthogonal codes</kwd>
  <kwd>Doppler sensitive</kwd>
  <kwd>side-lobes level</kwd>
  <kwd>adaptive clonal selection algorithm</kwd>
  <kwd>polyphase coded orthogonal signals</kwd>
  <kwd>aperiodic autocorrelation side lobe</kwd>
  <kwd>Doppler shift tolerance</kwd>
  <kwd>sustainable Doppler shifts</kwd>
  <kwd>Doppler tolerance performances</kwd>
 </kwd-group>

 <kwd-group kwd-group-type="Inspec-class">
  <compound-kwd>
   <compound-kwd-part content-type="code">B0260</compound-kwd-part>
   <compound-kwd-part content-type="text">Optimisation 
    techniques</compound-kwd-part>
  </compound-kwd>
  <compound-kwd>
   <compound-kwd-part content-type="code">B6140</compound-kwd-part>
   <compound-kwd-part content-type="text">Signal processing and 
    detection</compound-kwd-part>
  </compound-kwd>
  <compound-kwd>
   <compound-kwd-part content-type="code">B6320</compound-kwd-part>
   <compound-kwd-part content-type="text">Radar equipment, systems 
    and applications</compound-kwd-part>
  </compound-kwd>
 </kwd-group>
</article-meta>
...
Including Japanese 
...
<article-meta>
 ...  
 <kwd-group xml:lang="en">
  <kwd>heated air</kwd>
 </kwd-group>

 <kwd-group xml:lang="ja">
  <kwd>加温空気</kwd>
 </kwd-group>
 ...  
</article-meta>
...
Nested keywords
In section metadata, to provide navigation for an app
...
<sec>
 <sec-meta>
  <kwd-group specific-use="mobile-nav">
   <nested-kwd>
    <kwd>dosing</kwd>
    <nested-kwd>
     <kwd>geriatric</kwd>
     <nested-kwd>
      <kwd>Digoxin</kwd>
     </nested-kwd>
    </nested-kwd>
   </nested-kwd>
  </kwd-group>
  
  <kwd-group specific-use="mobile-nav">
   <nested-kwd>
    <kwd>Digoxin</kwd>
    <nested-kwd>
     <kwd>dosing</kwd>
     <nested-kwd>
      <kwd>geriatric</kwd>
     </nested-kwd>
    </nested-kwd>
   </nested-kwd>
  </kwd-group>
 </sec-meta>
 <title>Dosing Table, Geriatric</title>
 ...
</sec>
...
With vocabulary attributes 
...
<kwd-group kwd-group-type="physh" xml:lang="en"
  vocab="PhySH" vocab-identifier="https://physh.org/">
 <nested-kwd>
  <kwd content-type="facet" 
    vocab="PhySH" vocab-identifier="https://physh.org/" 
    vocab-term-identifier="https://physh.aps.org/browse?facetIds=Research%2520Areas"
   >Research Areas</kwd>
  <nested-kwd>
   <kwd content-type="concept" 
     vocab="PhySH" vocab-identifier="https://physh.org/"
     vocab-term-identifier="https://doi.org/10.29172/ba7ccb8ed7eb4e6f9c1eb622f5b4e242"
    >Atomic &amp; molecular processes in external fields</kwd>
   <nested-kwd>
    <kwd content-type="concept" 
      vocab="PhySH" vocab-identifier="https://physh.org/"
      vocab-term-identifier="https://doi.org/10.29172/da893accf204480b8a7e386479c50687"
     >Coherent control</kwd>
   </nested-kwd>
  </nested-kwd>
 </nested-kwd>
 <nested-kwd>
  <kwd content-type="facet" 
    vocab="PhySH" vocab-identifier="https://physh.org/"
    vocab-term-identifier="https://physh.aps.org/browse?facetIds=Physical%2520Systems"
   >Physical Systems</kwd>
  <nested-kwd>
   <kwd content-type="concept" 
     vocab="PhySH" vocab-identifier="https://physh.org/"
     vocab-term-identifier="https://doi.org/10.29172/bd252d88a60848979416daf84dee7f6b"
    >Atomic Systems</kwd>
   <nested-kwd>
    <kwd content-type="concept" 
      vocab="PhySH" vocab-identifier="https://physh.org/"
      vocab-term-identifier="https://doi.org/10.29172/42e66168abfd4328aa9df6fc3a077f75"
     >Molecules</kwd>
   </nested-kwd>
  </nested-kwd>
 </nested-kwd>
</kwd-group>
...
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