SubjectPractices

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Note: Summary of best practices added. Jenn Riley 10/12/05

[edit] Recording Subjects in OAI Records

[edit] Summary of Best Practices

• Choose subject values from relevant controlled vocabularies consistently and explicitly.
• Repeat subject information in more specific fields when they are available in the metadata format being used.
• Express multiple subjects in repeated fields.

[edit] Choice and Format of Subjects

In addition to the guidelines presented in this section, the Research Libraries Group Descriptive Metadata Guidelines for RLG Cultural Materials contains advice on the use of subject headings in metadata records.

Best

The best practice for subjects in shareable metadata is to use relevant controlled vocabularies consistently and explicitly. The controlled vocabularies chosen (there may be more than one used) should be relevant to the resource and known to the community to which the resources described would hold the most interest. The metadata format(s) used should allow the unambiguous specification of the vocabulary serving as the source of the subject headings applied to OAI records. (Note that simple Dublin Core does not allow controlled vocabularies to be specified; this is another argument for exposure of metadata formats in addition to DC records). The use and specification of a controlled subject vocabulary allows an OAI service provider to provide improved search services and to build browse indexes - particularly among all data providers using the same controlled vocabulary.

Depending on the materials being described, vocabularies such as the Library of Congress Subject Headings (LCSH), National Library of Medicine's Medical Subject Headings (MeSH), Sears List of Subject Headings, the Library of Congress Thesaurus for Graphic Materials I: Subject Terms (TGM I), or the Getty Art & Architecture Thesaurus (AAT) might be good choices. The most specific subject term available in the vocabulary should be applied.

Metadata authors may also wish to supply uncontrolled terms. This should be done as a supplement to a controlled vocabulary.

When using a precoordinated subject system such as LCSH, repeat any information that may also belong in other fields in the metadata record (e.g., geographic place) in the appropriate, more specific field. For example:

        <dc:subject>Gardening--Florida--History</dc:subject>
        <dc:coverage>Florida</dc:coverage>

Apply as many subject terms as necessary to describe the item in question. Place each subject term in its own element rather than placing multiple values within a single element (when using a metadata scheme that allows repeating elements). Placing multiple terms in a single element makes it more difficult for a service provider to index the terms contained within it individually.

Example of multiple subjects in separate subject fields:

         <dc:title>Map and profile of the proposed Paterson and Dover Rail Road and Paterson and
           Ramapo Rail Road.</dc:title>
         <dc:subject>Paterson and Ramapo Rail Road.</dc:subject>
         <dc:subject>Railroads--New Jersey--Maps.</dc:subject>
         <dc:subject>Iron industry and trade--New Jersey--Maps.</dc:subject>
         <dc:subject>Paterson and Dover Railroad.</dc:subject>

See DC LOC Map 1 for the complete record from which this example was taken.

Example of multiple subject fields in a single entry. This is not good practice -- the multiple subject headings will need to be pulled apart by the service provider:

   <dc:title>Vice-President Nixon Watches Devil Dance During a Roadside Stop</dc:title>
   <dc:subject>Nixon, Richard M. (Richard Milhous), 1913-; Dancers; Folk dancing; Clothing
       & dress; Vice presidents</dc:subject>

See DC Indiana Historical Society Photo 1 for the complete record from which this example was taken.

Good

When using only the required minimum Simple Dublin Core (oai_dc) or another format that does not allow the specification of the source of subject vocabulary, the next best option is to apply terms from a single standard controlled vocabulary consistently within an OAI set or an entire repository, and specify the vocabulary within the set description SetPractices or Identify response. See Providing Supplemental Documentation to OAI Service Providers. Metadata authors may also wish to supply uncontrolled terms. This should be done as a supplement to a controlled vocabulary.

Adequate

At minimum, a metadata provider should provide subject access via a local vocabulary or list used consistently across an OAI set or repository and to specify the vocabulary within the set description SetPractices or Identify response. See Providing Supplemental Documentation to OAI Service Providers. Metadata authors may also wish to supply uncontrolled terms. This should be done as a supplement to a controlled vocabulary.