Dublin Core - the topic of the resource. Typically, the topic will be represented using keywords, key phrases, or classification codes. Recommended best practice is to use a controlled vocabulary. To describe the spatial or temporal topic of the resource, use the Coverage element.


  • NSDL usage - the topic area, focus, theme or content matter of a resource
  • Field usage - strongly recommend
  • Number of occurrences - repeat the field as necessary

Controlled vocabulary

A specific NSDL controlled vocabulary is not used because:

  • the NSDL has grown beyond the ability of a simple, single vocabulary list being capable of effectively describing the entire scope of the library
  • many contributors (including Pathways) use subject-oriented vocabularies specific to their audiences and combining such lists into a NSDL supported controlled vocabulary is not practical in terms of scale or organization of such a list
  • resources are not available to formulate and maintain a subject list (if a list is deemed practicable) that would encompass the NSDL scope

Rather use the following recommendations for creating metadata for the subject field:

  • Use keywords or short phrases extensively
  • Pathways and other contributors continue to use existing controlled vocabularies (e.g. Library of Congress)
  • Pathways and other contributors continue to use their own controlled vocabularies. Terms from some Pathway vocabularies are below.

The controlled vocabularies of Pathways and other contributors are treated as free-text keywords within the subject field. That is, a method does not exist in the XML of the NSDL_DC metadata framework to indicate that a Pathway or other controlled vocabulary is being used.

Cataloging best practices

  • Include terms that describe the predominant content of the resource.
  • Include terms that describe the resource in the context of science, technology, engineering and mathematics education and research.
  • Choose significant and unique words.
  • Avoid words that are too general to describe a particular item.
  • Provide sufficient terms to facilitate discovery.
  • Do not repeat variations of terms, synonyms, case or tense variations or alternate spellings.

Use and resource examples

XML tips and examples

  • When using local vocabulary terms, do not use the any refinement in XML documents.

<dc:subject xsi:type="dct:LCC">Agriculture</dc:subject> this is not XML schema enforced for LCC 
<dc:subject xsi:type="dct:LCC">Animal culture </dc:subject> this is not XML schema enforced for LCC 
<dc:subject>put any keyword here</dc:subject> 
<dc:subject>or keyword phase</dc:subject> 
<dc:subject>stratus clouds</dc:subject>

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