<subject> Subject Name

Name of one overarching category, broad classification, topic, or theme used to describe a standards document, as a higher-level descriptor of its content.


In JATS (the specification on which NISO STS was based), subjects are used to organize articles in a Table of Contents or similar. In standards documents, subjects have been used to organize standards into series or provide category classing. The source of the subjects can be a classification scheme, such as a taxonomy (ISO STD 25964:-1:ed-1:2011 https://www.iso.org/obp/ui/#iso:std:iso:25964:-1:ed-1:v1:en:term:2.6).
Language in Subjects
Subject elements are contained in <subj-group> elements. There may be several <subj-group>s, each of which can be identified separately by language, vocabulary, or taxonomy source. None of the individual subject elements (<subject> and <compound-subject>) take the @xml:lang attribute; that is reserved for the group level (<subj-group>). This means that if there are subjects in several languages they should be in different <subj-group>s.
Vocabulary Attributes
For controlled vocabularies, two attributes can be used to link a subject term to its source:
  • @vocab-term — This attribute holds the canonical form of the subject term as expressed in the vocabulary named on the <subj-group> element. The content of the subject element (<subject> or <compound-subject>) might not be exactly the same as the canonical form, as the <subject> content might be a user-specific variant.
  • @vocab-term-identifier — This attribute holds a unique identifier and possible pointer to the specific subject term in the named vocabulary. While this is typically a URI or DOI reference, the @vocab-term-identifier could be an item number or other system-specific identifier.

Vocabulary Attributes Best Practice

If the subject terms in a <subj-group> come from a controlled vocabulary, taxonomy, ontology, database, term list, or similar formally defined term source, the @vocab attribute (and if possible, the @vocab-identifier attribute) should be used on the <subj-group> element to name the source.
If this source of terms uses a subject-term-specific identifier, then also record the specific term using the @vocab-term and @vocab-term-identifier attributes on the subject term (<subject>). If the <subj-group> does not include the vocabulary identification attributes, those attributes (@vocab and @vocab-identifier) may also be used on the <subject> element.
If the subject terms come from, or are specific to, a field of study that can be named (particularly where different fields might define the same term differently), name the field of study in the @subj-group-type attribute (“structural engineering”, “mechanical engineering”, “bird watching”). Such terms are typically, but not always, informally defined.
Although subject terms may be from an uncontrolled vocabulary, this is less likely than for terms such as keywords, since subject codes such as IPC, UNSPSC, UNS, etc. are controlled by defined vocabularies. If the subject terms are uncontrolled, either omit the @vocab attribute on <subj-group> or use the value “uncontrolled”.
Related Elements
Types of Subjects: This Tag Set contains several differently-structured types of subject elements:
  • <subject> is used with simple subjects: words or phrases.
  • <compound-subject> is used with multi-part subjects, such as a subjects that contains both a code and its description/name/title.
  • <ics>Used to hold ICS terms, which are a special kind of subjects that are not tagged as <subject>s, but rather use their own specific elements (<ics-wrap>, <ics>, and <ics-desc>).
Keywords vs Subjects Terms: Subject terms (collected within a <subj-group> element) name broad classifications, categories, topics, or themes that describe or classify a standard. Keywords (collected within a <kwd-group> element) contain words from the narrative text or words (such as broader and narrower terms) related to that text.

Base Attributes

Models and Context
May be contained in
Content Model
<!ELEMENT  subject      (#PCDATA %subject-elements;)*                >
Expanded Content Model

(#PCDATA | bold | fixed-case | italic | monospace | num | overline | roman | sans-serif | sc | strike | underline | ruby | alternatives | inline-graphic | inline-media | private-char | chem-struct | inline-formula | named-content | styled-content | sub | sup)*

Tagged Samples
Subjects from SDO-specific taxonomy showing vocabulary attributes
<subj-group id="SG1.1" originator="ASME" vocab="ASME-Taxonomy"
  xml:lang="en" subj-group-type="Industries"
 <subject id="SG1.1-1"
  >Fossil Power</subject>
 <subject id="SG1.1-2"
  >Power Plants</subject>

<subj-group id="SG1.2" originator="ASME" vocab="ASME-Taxonomy"
  xml:lang="en" subj-group-type="Materials-Product-Form"
 <subject id="SG1.2-1"
 <subject id="SG1.2-2"
  >Pressure Vessels</subject>
Subject from Dewey Decimal showing canonical term in @vocab-term attribute and its translation in subject content (Note “Engineering of railroads, roads” is DDC term, not free text.)
<subj-group id="DDC-ex1" vocab="DDC" vocab-identifier="DDC23" xml:lang="en">
 <subject id="DCC-625" vocab-term="Engineering of railroads, roads"
  Ingénierie des chemins de fer, routes</subject>