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GILS and Dublin Core (DC)

The following text has been circulated for comment in both the DC and GILS communities. All respondents agreed that this statement correctly states the relationship between GILS and Dublin Core.

Background: Both the Global Information Locator Service (GILS) and the Dublin Core (DC) have been in wide use for several years, often within the same application communities. Those who have used both in combination recognize that the two are complementary, but others may have some confusion about one or the other. This joint statement agreed among the GILS and DC communities is meant to dispel such confusion.

Scope: GILS and DC agree that metadata can characterize virtually anything, not only automated information but physical objects, people, events, etc. GILS and DC both focus on descriptive metadata, with particular emphasis on the metadata used in networked information discovery.

Diversity: There is great diversity in the kinds of metadata in use, and this diversity often reflects the distinct needs of different communities of interest. GILS and DC are both opposed to any loss of information or precision in existing metadata merely to accommodate a secondary use such as cross-domain searching.

Semantic Interoperability: It is often the case that the skills or expectations of a user are different than those anticipated by the provider of an information resource. For instance, a provider may offer search across three kinds of resources: book citations, news articles, and e-mail messages. If the searcher expects to search by "title", the book citations are obviously searchable, but the provider has to decide what characteristic is semantically equivalent to "title" for the other collections. In the news article collection, "headline" might be considered semantically equivalent to "title" while "subject" might be the semantic equivalent in the e-mail messages. GILS and DC agree that semantic interoperability is essential for coherent search across diverse metadata.

Bibliographic Interoperability: Bibliographic techniques and systems come from a long tradition of semantic interoperability and are among the most precious of the common heritage of all peoples. In recent decades, the worldwide bibliographic communities have standardized Machine Readable Cataloging (MARC). GILS and DC agree that new search approaches must preserve interoperability with the common bibliographic concepts used in bibliographic settings, including interoperability with MARC elements such as Title, Author, Subject, Publisher, and Publication Date. (The fifteen unqualified Dublin Core elements are mapped to concepts used in GILS by the Library of Congress Network Development and MARC Standards Office, available at <http://www.loc.gov/marc/dccross.html> ).

Extensibility: DC and GILS have both found wide application by various communities that have taken advantage of their designed extensibility provisions. GILS is extended either by specifying Usage Guidelines (e.g., U.S. Federal GILS, Global Environmental Information Locator Service) or by adding specifications onto the GILS specification (e.g, the Geospatial Profile is a superset of the GILS Profile). DC elements can be qualified to make additional elements, and the set of elements in any particular community can be supplemented by elements not specified in DC.

Compliance: GILS specifies compliance in terms of an Internet server supporting these nine search concepts: Title, Author-name corporate, Distributor Name, Record Source, Date/Time Last Modified, Subject Terms Controlled, Subject Terms Uncontrolled, Local Control Number, and Any/Anywhere (full-text). Although DC suggests standard semantics for 15 common metadata elements, it does not specify a preferred syntax nor how the elements must be used in systems. (In practice, DC elements are often used in combination with either the W3C Recommendation concerning HTML Meta tags or the W3C Recommendation concerning Resource Description Framework.) GILS-compliant search is quite compatible with DC elements and the two are often found together in operational implementations of a search service.

Registration of Semantics: The International Organization for Standardization (ISO) has developed a good base for the registration of semantics. GILS and DC (version 1.1) have defined semantic elements using ISO/IEC 11179, "Information technology-- Specification and Standardization of Data Elements". This registration approach helps to highlight commonalties among diverse metadata and may also provide improved mechanisms for extensibility. Elements available for mapping to a presentation of records retrieved from a GILS-compliant server can be found following ISO 11179 in the ISO Basic Semantics Registry (see </bsr-gils.xsd> in XML Schema syntax; </bsr-gils.rdfs> in RDF Schema syntax). DC elements following ISO 11179 can be found at < http://purl.org/dc/documents/rec-dces-19990702.htm> .


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