Guidelines for using Agent Roles in Dublin Core (Draft)
An Appendix to: "Using Dublin Core"
1/23/04, dih
2/12/04, rsg
2/16/04, dih
9/2/04, dih
9/29/04, rsg
9/30/04, dih
Function of roles and history of approval by DCMI
The need to express a role for the "Agent" elements (Creator,
Contributor, and, to a lesser extent, Publisher) in the
Dublin Core element Set has been expressed for many years
and there have been a number of ideas proposed for how to
accommodate this need. A role is a term that further refines
the contribution of the agent to the resource described by
specifying the particular 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.
The DCMI Usage Board has discussed the issue several times
and agreed that the role values are properly element
refinements. At its meeting in Florence in Oct. 2002,
the Board generally agreed that deprecating Creator and
Publisher in favor of Contributor should be considered,
since the role values Creator and Publisher could be used to
refine Contributor if needed. Because of negative response to
this sort of change in the Dublin Core element set, the DCMI
Usage Board decided to recommend role refinements only to
Contributor, but to leave Creator, Contributor and Publisher
as separate elements.
Because a standardized, widely adopted list of roles already
existed in the MARC Code List for Relators, it was recommended
early in these discussions that DCMI not develop its own. In
early 2000 a subset of the MARC relators list was circulated
for approval to include 10 generally applicable roles out
of the approximately 150 MARC relator terms. Because of the
need to consider other aspects of the "Agent" issue, at that
time the proposal was deferred. Discussion initially in the
DC-Libraries Working Group (which prepared an application
profile for use in libraries that included the relator terms)
and later in the DCMI Usage Board revealed that consensus was
that users not be constrained by a too-small list of elements
and that the entire list of relator terms should be considered
given the difficulty of anticipating needs in various domains.
However, as the UB evaluated the terms on the list, it became
clear that the full list included terms that extended beyond
the scope of the semantics of dc:contributor. The UB agreed
that, in principle and practice, refinements of elements (as
sub-properties) must in every case be a valid sub-property
by refining rather than extending the semantics of that
element or property. The obvious solution was to specify
which terms are subproperties of dc:contributor by falling
under the definition of “an entity responsible for making
contributions to the content of the resource. Also needed
was a process to continue to evaluate new terms added by LC
to their list on the basis of this requirement.
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. As an
example:
Original term Dumb-down "Simple DC"
marcrel:degreeGrantor marcrel:degreeGrantor ---
marcrel:owner marcrel:owner ---
marcrel:illustrator dc:contributor dc:contributor
Thus, in the context of DC record based on an application
profile using MARC relator terms, usage of roles not on the
valid sub-property list 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 Library of Congress has prepared an RDF expression of the
MARC relator list, to be used in conjunction with the Dublin
Core element Contributor. The document contains assertions as
to whether or not the particular role term is a subproperty
of dc:contributor as follows:
.
The MARC Relator list, what it is and how it's structured
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 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 (dc:description).
Terms that do not contain the assertion that they are
a subproperty of contributor are not to be considered
a refinement of dc:contributor. In determining whether
the subproperty assertion applies LC and the Usage Board
took a fairly narrow view. The assertion is included only
if that contribution always was in terms of the content
of the resource. For example, "binder" does not have the
subproperty 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.
Using Roles with Contributor
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.
An assertion is made that marcrel:publisher is equivalent to
dc:publisher; in this instance publisher may or may not also be
a contributor to the resource so the subproperty of contributor
assertion is not made. In the case of marcrel:creator,
an assertion is made that it is equivalent to dc:creator.
If marc:creator is used instead of dc:creator, this should
be done consistently-- the two terms should probably not be
used together in the same instance. In addition, the term
"depicted" is considered a subproperty of dc:subject and
"distributor" a subproperty of dc:published; in these cases
this assertion is made.
Because roles are to be used only with the Contributor element,
appropriate "Dumb Down" of all 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.
Using Roles in XML and other Schemas
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 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.
Terms not on the MARC Relators list
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. Another alternative is to present a proposal
to the DCMI Usage Board to define a new refinement within the
dc:terms namespace, if such refinement meets the given criteria
for being cross-domain and needed for resource discovery.
Managing the Use of Role in an Implementation
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.