Subject

Subject

The topic of the resource. Typically, a Subject will be expressed as keywords, key phrases or classification codes that describe the intellectual content of the resource.

Mandatory when applicable

In the DC subject element two kinds of values are possible: encode either a keyword or a classification. When both are available use separate occurrences of this element.
Use the first occurrence of the DC element 'subject' for a human readable keyword.
In general, choose the most significant and unique words for keywords, avoiding those too general to describe a particular resource. If the subject of the resource is a person or an organization, use the same form of the name as you would if the person or organization were an author, but do not repeat the name in the dc:creator element.
For keywords/keyphrases that are not controlled by a vocabulary or thesaurus either encode multiple terms with a semi-colon separating each keyword/keyphrase; or repeat the element for each term. There are no requirements regarding the capitalization of keywords though internal (within archive) consistency is recommended.
Where terms are taken from a standard classification schema: encode each term in a separate element. Encode the complete subject descriptor according to the relevant scheme. Use the capitalisation and punctuation used in the original scheme.
It is recommended to use an URI when using classification schemes or controlled vocabularies especially when codified schemes are used DDC or UDC. Service providers can recognise encoding schemas more easy when the schema is "URI-fied" by an authority namespace. When the classification scheme is codified, use a human readable text of the code, preferably in English, directly below the codified element. For example:

<dc:subject>info:eu-repo/classification/ddc/641</dc:subject>
<dc:subject>Anatomy</dc:subject>

If no specific classification scheme is used we recommend the Dewey Decimal Classification (DDC). The first 1000 terms is called the Dewey Decimal Classification Summary and can be downloaded at http://www.oclc.org/dewey/resources/summaries/ if one agrees with the following terms and conditions:
http://www.oclc.org/research/researchworks/ddc/terms.htm

• Type
  DC element 'subject' describes the topic(s) of an resource; DC element 'type' describes the kind of academic output / Publication Type the resource is a representation of.

More on subject classification, see the Subject classification page in chapter "Use of Vocabularies and Semantics".