NOTE: This text was last revised in 2005. As of 2011, a completely revised User Guide is being developed at the wiki page /archive/mediawiki_wiki/User_Guide. DCMI's Glossary and FAQ are also under revision.
|Is Replaced By:||http://dublincore.org/documents/2005/12/07/usageguide/appendix_roles.shtml|
|Is Part Of:||http://dublincore.org/documents/2005/11/07/usageguide/|
|Status of document:||DCMI Recommended Resource|
|Description of document:||This document describes the principles governing Dublin Core qualifiers, the two categories of qualifiers, and lists instances of qualifiers approved by the Dublin Core Usage Board as well as guidance for their use.|
Roles allow further explanation of the contribution of an agent to the resource described by specifying the particular nature of the contribution. An example is that "illustrator" might be a role associated with the element Contributor when that person provided illustrations to the resource rather than being responsible for other aspects of the intellectual content.
In Dublin Core, role values are properly element refinements, and are available only as refinements of the Contributor element. DCMI and the Library of Congress have cooperated to make a subset of the MARC Relator Terms available for re-use as role refinements by specifying which terms are sub-properties of dc:contributor by virtue of falling under the definition of "an entity responsible for making contributions to the content of the resource."
The MARC Code List for Relators was developed for use in MARC 21 bibliographic records to express the relationship between a name and a work. The list includes both role terms and three-character codes that represent those terms. The terms were only included on the list when the name and its associated role were considered important enough to include on a bibliographic record as an access point. The Library of Congress is the maintenance agency for this list and regularly adds new ones when the need is expressed and documented. The agreement between DCMI and the Library of Congress specifies that new terms submitted to LC will be referred to the DC Usage Board to endorse assertions that the term can be used as a refinement of dc:contributor.
The MARC Relator list includes three-character alphabetic codes to be used to identify roles. These are to be considered synonyms for the term they represent. In addition the list provides definitions for use of the term/code. In the RDF representation, the codes are tokens to be used for the term and are part of the URI. In some cases unused terms refer to used terms; these are included in the RDF representation as a note.
Terms that do not contain the assertion that they are a sub-property of contributor are not to be considered a refinement of dc:contributor. In determining whether the sub-property assertion applies, LC and the Usage Board took a fairly narrow view. The assertion is included only if that contribution always applies in terms of the content of the resource. For example, "binder" does not have the sub-property assertion, since it depends upon what the resource is; sometimes a binder may contribute to the content if the item is valued as an art object, while in other instances, the binder has not contributed to content.
In order to minimize the possibility of confusion, the Usage Board has authorized the use of roles only with the element Contributor. Because Creator is in some sense a role elevated to a position at the level of element, the Board's position is that it makes no sense to provide yet another level of roles beneath that particular element.
Other assertions are also made: that marcrel:publisher refines dc:publisher; in this instance publisher may or may not also be a contributor to the resource so the sub-property of contributor assertion is not made. In the case of marcrel:creator, an assertion is made that it is a sub-property of both dc:creator and dc:contributor. In addition, the term "depicted" is considered a sub-property of dc:subject and "distributor" a sub-property of dc:publisher; in these cases this assertion is made.
Because roles are generally used only with the Contributor element, appropriate "Dumb Down" of most agent refinements expressed as roles will be to Contributor. Given this, implementors may choose (preferably within the context of an application profile), to specify explicitly whether the MARC relator term of creator should be used, based on the fact that the distinction could be retained in Simple Dublin Core if the Element level term is retained for those particular roles.
Because the maintenance of the MARC Relator list will remain with the Library of Congress, the namespace of the roles will be established by LC and will not be a DCMI namespace. Thus, schemas or instances will need to include the MARC relator namespace in order to properly express role terms. See the document "Guidelines for Implementing Dublin Core in XML" for specific information on using non-DCMI namespaces.
The Library of Congress has prepared an RDF expression of the MARC relator list, to be used in conjunction with the Dublin Core elements. The document contains assertions as to whether or not the particular role term is a sub-property of a DC term using the following pattern:
<rdfs:sub-propertyOf rdf:resource="http://purl.org/dc/elements/1.1/contributor" />
A document containing additional technical information about the use of MARC Relator terms as well as examples of usage in XML, XHTML and RDF/XML can be found at: http://www.ukoln.ac.uk/metadata/dcmi/marcrel-ex/
The MARC Relator list has been developed over many years to meet a wide variety of needs. New terms are added on the basis of need, and LC has expressed willingness to continue to expand the list upon request. Implementers also have the option to create and expose alternative vocabularies for the expression of other kinds of roles not reflected in the MARC Relator list.
For those implementations wishing to use terms from the MARC relators list that do not have a sub-property relationship to dc:contributor, it should be noted that an implementation may use these terms with no intrinsic harm to interoperability by using those terms directly as MARC relator terms.
Thus, in the context of DC record based on an application profile using MARC relator terms, usage of roles not on the list of valid sub-properties approved by DC could be used in a Qualified DC expression, but not in a Simple DC expression, according to the rules for dumb-down.
The full MARC Relator list includes approximately 150 separate terms for various roles. A subset is provided here for use with dc:contributor. Even within this subset some of the roles on the list were created for specific domains and would be of little use in other communities. It might therefore be useful for implementations to declare a further subset of the role vocabulary as relevant to their specific goals, preferably by way of a formal application profile.
The full list (with reference to DC refinements): http://www.loc.gov/loc.terms/relators/dc-relators.html
The subset defining only those refining DC terms: http://www.loc.gov/loc.terms/relators/dc-contributor.html
The RDF markup: http://www.loc.gov/loc.terms/relators/dc-relators.xml