Dublin Core Workshop Series S. Weibel Internet-Draft J. Kunze draft-kunze-dc-02.txt C. Lagoze 10 February 1998 Expires in six months Dublin Core Metadata for Simple Resource Discovery 1. Status of this Document This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as ``work in progress.'' To learn the current status of any Internet-Draft, please check the ``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Distribution of this document is unlimited. Please send comments to weibel@oclc.org, or to the discussion list meta2@mrrl.lut.ac.uk. 2. Introduction Finding relevant information on the World Wide Web has become increasingly problematic in proportion to the explosive growth of networked resources. Current Web indexing evolved rapidly to fill the demand for resource discovery tools, but that indexing, while useful, is a poor substitute for richer varieties of resource description. An invitational workshop held in March of 1995 brought together librarians, digital library researchers, and text-markup specialists to address the problem of resource discovery for networked resources. This activity evolved into a series of related workshops and ancillary activities that have become known collectively as the Dublin Core Metadata Workshop Series. The goals that motivate the Dublin Core effort are: - Simplicity of creation and maintenance - Commonly understood semantics - International scope and applicability - Extensibility - Interoperability among collections and indexing systems These requirements work at cross purposes to some degree, but all are desirable goals. Much of the effort of the Workshop Series has been directed at minimizing the tensions among these goals. One of the primary deliverables of this effort is a set of elements that are judged by the collective participants of these workshops to be the core elements for cross-disciplinary resource discovery. The term ``Dublin Core'' applies to this core of descriptive elements. Early experience with Dublin Core deployment has made clear the need to support additional qualification of elements for some applications. Thus, Dublin Core elements may be expressed in simple unqualified ways that minimal discovery and retrieval tools can use, or they may be expressed with additional structure to support semantics-sharpening qualifiers that minimal tools can safely ignore but that more complex tools can employ to increase discovery precision. The broad agreements about syntax and semantics that have emerged from the workshop series will be expressed in a series of five Informational RFCs, of which this document is the first. These RFCs (currently they are Internet-Drafts) will comprise the following documents. 2.1. Dublin Core Metadata for Simple Resource Discovery An introduction to the Dublin Core and a description of the semantics of the 15-element Dublin Core element set without qualifiers. This is the present document. 2.2. Encoding Dublin Core Metadata in HTML A formal description of the convention for embedding unqualified Dublin Core metadata in an HTML file. 2.3. Qualified Dublin Core Metadata for Simple Resource Discovery The principles of element qualification and the semantics of Dublin Core metadata when expressed with a recommended qualifier set known as the Canberra Qualifiers. 2.4. Encoding Qualified Dublin Core Metadata in HTML A formal description of the convention for embedding qualified Dublin Core metadata in an HTML file. 2.5. Dublin Core on the Web: RDF Compliance and DC Extensions A formal description for encoding Dublin Core metadata with qualifiers in RDF (Resource Description Framework) [1] compliant metadata, and how to extend the core element set. 3. Description of Dublin Core Elements The following is the reference definition of the Dublin Core Metadata Element Set. The evolving reference description, including any defined qualifiers, resides at [2]: http://purl.org/metadata/dublin_core In the element descriptions below, each element has a descriptive name intended to convey a common semantic understanding of the element, as well as a formal single-word label intended to make the syntactic specification of elements simpler for encoding schemes. Although some environments, such as HTML, are not case-sensitive, it is recommended best practice always to adhere to the case conventions in the element labels given below to avoid conflicts in the event that the metadata is subsequently extracted or converted to a case-sensitive environment, such as XML (Extensible Markup Language) [3]. Each element is optional and repeatable. Furthermore, metadata elements may appear in any order, and with no significance being attached to that order. To promote global interoperability, a number of the element descriptions suggest a controlled vocabulary for the respective element values. It is assumed that other controlled vocabularies will be developed for interoperability within certain local domains. A metadata element's meaning is unaffected by whether or not the element is embedded in the resource that it describes. The metadata elements fall into three groups which roughly indicate the class or scope of information stored in them: (1) elements related mainly to the Content of the resource, (2) elements related mainly to the resource when viewed as Intellectual Property, and (3) elements related mainly to the Instantiation of the resource. Content Intellectual Property Instantiation ----------- --------------------- ------------- Title Creator Date Subject Publisher Type Description Contributor Format Source Rights Identifier Language Relation Coverage 3.1. Title Label: "Title" The name given to the resource, usually by the Creator or Publisher. 3.2. Author or Creator Label: "Creator" The person or organization primarily responsible for creating the intellectual content of the resource. For example, authors in the case of written documents, artists, photographers, or illustrators in the case of visual resources. 3.3. Subject and Keywords Label: "Subject" The topic of the resource. Typically, subject will be expressed as keywords or phrases that describe the subject or content of the resource. The use of controlled vocabularies and formal classification schemes is encouraged. 3.4. Description Label: "Description" A textual description of the content of the resource, including abstracts in the case of document-like objects or content descriptions in the case of visual resources. 3.5. Publisher Label: "Publisher" The entity responsible for making the resource available in its present form, such as a publishing house, a university department, or a corporate entity. 3.6. Other Contributor Label: "Contributor" A person or organization not specified in a Creator element who has made significant intellectual contributions to the resource but whose contribution is secondary to any person or organization specified in a Creator element (for example, editor, transcriber, and illustrator). 3.7. Date Label: "Date" A date associated with the creation or availability of the resource. Such a date is not to be confused with one belonging in the Coverage element, which would be associated with the resource only insofar as the intellectual content is somehow about that date. Recommended best practice is defined in a profile of ISO 8601 [4] that includes (among others) dates of the forms YYYY and YYYY-MM-DD. In this scheme, for example, the date 1994-11-05 corresponds to November 5, 1994. 3.8. Resource Type Label: "Type" The category of the resource, such as home page, novel, poem, working paper, technical report, essay, dictionary. For the sake of interoperability, Type should be selected from an enumerated list that is currently under development in the workshop series. 3.9. Format Label: "Format" The data format of the resource, used to identify the software and possibly hardware that might be needed to display or operate the resource. For the sake of interoperability, Format should be selected from an enumerated list that is currently under development in the workshop series. 3.10. Resource Identifier Label: "Identifier" A string or number used to uniquely identify the resource. Examples for networked resources include URLs and URNs (when implemented). Other globally-unique identifiers, such as International Standard Book Numbers (ISBN) or other formal names are also candidates for this element. 3.11. Source Label: "Source" Information about a second resource from which the present resource is derived. While it is generally recommended that elements contain information about the present resource only, this element may contain a date, creator, format, identifier, or other metadata for the second resource when it is considered important for discovery of the present resource; recommended best practice is to use the Relation element instead. For example, it is possible to use a Source date of 1603 in a description of a 1996 film adaptation of a Shakespearean play, but it is preferred instead to use Relation "IsBasedOn" with a reference to a separate resource whose description contains a Date of 1603. Source is not applicable if the present resource is in its original form. 3.12. Language Label: "Language" The language of the intellectual content of the resource. Where practical, the content of this field should coincide with RFC 1766 [5]; examples include en, de, es, fi, fr, ja, th, and zh. 3.13. Relation Label: "Relation" An identifier of a second resource and its relationship to the present resource. This element permits links between related resources and resource descriptions to be indicated. Examples include an edition of a work (IsVersionOf), a translation of a work (IsBasedOn), a chapter of a book (IsPartOf), and a mechanical transformation of a dataset into an image (IsFormatOf). For the sake of interoperability, relationships should be selected from an enumerated list that is currently under development in the workshop series. 3.14. Coverage Label: "Coverage" The spatial or temporal characteristics of the intellectual content of the resource. Spatial coverage refers to a physical region (e.g., celestial sector); use coordinates (e.g., longitude and latitude) or place names that are from a controlled list or are fully spelled out. Temporal coverage refers to what the resource is about rather than when it was created or made available (the latter belonging in the Date element); use the same date/time format (often a range) [4] as recommended for the Date element or time periods that are from a controlled list or are fully spelled out. 3.15. Rights Management Label: "Rights" A rights management statement, an identifier that links to a rights management statement, or an identifier that links to a service providing information about rights management for the resource. 4. Security Considerations The Dublin Core element set poses no risk to computers and networks. It poses minimal risk to searchers who obtain incorrect or private information due to careless mapping from rich data descriptions to simple Dublin Core scheme. No other security concerns are likely to be raised by the element description consensus documented here. 5. References [1] Resource Description Framework (RDF) Model and Syntax, http://www.w3.org/TR/WD-rdf-syntax [2] Dublin Core Metadata Element Set: Reference Description, http://purl.org/metadata/dublin_core [3] Extensible Markup Language (XML), http://www.w3.org/TR/PR-xml [4] Date and Time Formats (based on ISO 8601), W3C Technical Note, http://www.w3.org/TR/NOTE-datetime [5] RFC 1766, Tags for the Identification of Languages, http://ds.internic.net/rfc/rfc1766.txt 6. Authors' Addresses Stuart L. Weibel OCLC Online Computer Library Center, Inc. Office of Research 6565 Frantz Rd. Dublin, Ohio, 43017, USA Email: weibel@oclc.org Voice: +1 614-764-6081 Fax: +1 614-764-2344 John A. Kunze Center for Knowledge Management University of California, San Francisco 530 Parnassus Ave, Box 0840 San Francisco, CA 94143-0840, USA Email: jak@ckm.ucsf.edu Voice: +1 415-502-6660 Fax: +1 415-476-4653 Carl Lagoze Digital Library Research Group Department of Computer Science Cornell University Ithaca, NY 14853, USA Email: lagoze@cs.cornell.edu Voice: +1-607-255-6046 Fax: +1-607-255-4428