Internet-Draft R. Iannella draft-iannella-admin-01.txt DSTC 30 June 1999 D. Campbell Expires in six months NLA ** To be submitted to the IETF ** The A-Core: Metadata about Content Metadata 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 rendered obsolete 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 view the entire list of current Internet-Drafts, please check the "1id- abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu US West Coast). Distribution of this document is unlimited. Please send comments to . 2. Introduction Metadata about metadata - referred to as the A-Core - is useful to designate information about the provenance, management or administration of other sets of descriptive metadata. The objective of A-Core is to provide simple verification of the integrity, ownership, and authorship of metadata retrieved from networked resources. The A-Core elements are utilised to associate the instruments (who, what) with the events (when) of the process of metadata management. It is important to recognise that the A-Core is an "accessory" metadata element set as opposed to a "content" metadata element set - its purpose is to be used by systems and users to determine the currency and integrity of content metadata, and provide details on how to contact entities involved with the management of content metadata. The relationship between A-Core and content metadata is shown below in Figure 1. __________ __________ __________ | | describes | Content | describes | A-Core | | Resource | <--------- | Metadata | <--------- | Metadata | |__________| |__________| |__________| Figure 1 - A-Core Model In Figure 1, we differentiate A-Core from other metadata element sets by the role it plays. A-Core metadata describes content metadata which, in turn, describes resources. Examples of content metadata include the Dublin Core [1], the Education Network of Australia schema [2] and the Australian Government Locator Service [9] metadata. The A-Core, as with other metadata elements sets, is a "core" set. That is, it is extensible by allowing the addition of new elements that are specific to a community's needs. This is similar to the model presented by the Dublin Core Metadata Element Set [1]. The A-Core is not useful by itself. It must be used in association with at least one content metadata element set. This conjunction of different metadata sets is supported by a number of metadata encoding systems, such as the Resource Description Framework [3] and the HTML META tag [4]. Examples are given in Section 5. 3. Description of A-Core Elements The following is the reference definition of the A-Core Metadata Element Set. The evolving reference description can be found at: http://metadata.net/ac There are four main categories of A-Core elements: 1 - Who, What, When 2 - Validity Dates 3 - Metadata Location 4 - Rights Ownership The specific definitions of the elements are described in the following sections. Each A-Core element is formally described using a set of nine attributes from the ISO 11179 standard [5]. These include: Name - The label assigned to the data element Identifier - The unique identifier assigned to the data element Version - The version of the data element Language - The language in which the data element is specified Definition - A statement that clearly represents the concept and essential nature of the data element Obligation - Indicates if the data element is required to always or sometimes be present (contain a value) Datatype - Indicates the type of data that can be represented in the Value of the data element Maximum Occurrence - Indicates any limit to the repeatability of the data element Comment - A remark concerning the application of the data element. Four of the above nine ISO 11179 attributes are common to all the A-Core elements. These are, with their respective values: Version: 2.0 Language: en Datatype: Character String Maximum Occurrence: Unlimited The above attributes will not be repeated in the definitions below, however, they do represent part of the formal element definitions. 3.1 Who, What, When A number of A-Core elements are defined to indicate: - Who was responsible, - What they did, and - When they did it. There are three elements for describing the characteristics of Who: - name: the entity responsible for the content metadata - email: electronic mail address for the Name - contact: mechanisms on how to contact the Name There is one element for describing the What: - activity: a defined action performed by Name on the content metadata There is one element for describing the When: - date: the date that the Activity occurred. For example: name: Crystal, Jacky email: jacky@metadata.net contact: Phone 555 11111 activity: created date: 1999-01-01 The above elements may be grouped in the case of multiple activities occurring on the same content metadata. Below are the formal definitions for the above elements. ----------------------------------------------------------------------- Name: Name Identifier: name Definition: The name of the entity responsible for undertaking a defined action on the content metadata Obligation: Mandatory Comment: Examples of Name include a person, an organisation, or a service. Where the person has an affiliation with an organisation, this information may be included. The name of a person should be provided in inverse order, that is, last name before firstname, with a comma separator. ----------------------------------------------------------------------- Name: Email Address Identifier: email Definition: Electronic Mail address for the responsible entity Obligation: Mandatory Comment: The email address must be encoded to be consistent with Internet Address standard RFC822 [6]. ----------------------------------------------------------------------- Name: Contact Information Identifier: contact Definition: Information on how to contact the responsible entity Obligation: Optional Comment: The information should be one or more of: a street or postal address, a telephone number, a facsimile number, or other forms of physical or electronic contact information. Links to full descriptions of the responsible entity may also be included, such as name registries. ----------------------------------------------------------------------- Name: Activity Identifier: activity Definition: The action performed on the content metadata by the responsible entity Obligation: Mandatory for the act of creation. Other actions are optional. Comment: The actions are taken from a non-exhaustive list including: "created", "modified" and "expired". Other sources may be used for the activity values such as codes from the USMARC Relator List [10] ----------------------------------------------------------------------- Name: Date of Activity Identifier: date Definition: The date on which the activity took place by the responsible entity Obligation: Mandatory for the act of creation. Other dates are optional. Comment: Encoded to the W3C Profile of ISO 8601 [7]. ----------------------------------------------------------------------- 3.2 Validity Dates There is one date element to indicate the time period for which the content metadata should be considered valid: - dateRange: The dates that the content metadata is valid For example: dateRange: 1999-01-01/1999-12-31 Below is the formal definition for the above element. ----------------------------------------------------------------------- Name: Valid Date Range Identifier: dateRange Definition: The start and/or end date of the validity of the content metadata Obligation: Optional Comment: Content metadata accessed outside the date ranges should be considered to be invalid. Encoded to the W3C Profile of ISO 8601 [7] including the use of the "/" to indicate the range scope. For example, "/1999-12-31" indicates validity up to 31 December 1999, "1999-01-01/" indicates validity from 1 January 1999 onwards, and "1999-01-01/1999-12-31 indicates validity between the two specified dates. ----------------------------------------------------------------------- 3.3 Metadata Location There is one element to indicate an identifier for the content metadata. - location: Reference information indicating the source of the metadata. For example: location: http://metadata.net/myreport.rdf Below is the formal definition for the above element. ------------------------------------------------------------------- Name: Metadata Location Identifier: location Definition: An unambiguous reference to the content metadata within a given context Obligation: Optional Comment: This element is used if the content metadata and A-Core metadata are not in the same location. Recommended best practice is to identify the content metadata by means of a string or number conforming to a formal identification system. Example formal identification systems include the Uniform Resource Identifier (URI) (including the Uniform Resource Locator (URL)) and the Digital Object Identifier (DOI). Other identifiers, such as local repository/database keys, may be used. ------------------------------------------------------------------- 3.4 Rights Ownership There is one element to indicate the rights owner for the content metadata. - rights: Reference to a rights management statement For example: Rights: Copyright metadata.net 1999 Below is the formal definition for the above element. ------------------------------------------------------------------- Name: Rights Ownership Identifier: rights Definition: Information about rights held in and over the content metadata Obligation: Optional Comment: Typically, the Rights element will contain a rights management statement for the content metadata, or refer to a service providing such information. ------------------------------------------------------------------- 4. A-Core Usage Scenario A publisher launches an e-journal on the Web. Each article in the e-journal is separately described by the publisher using Dublin Core content metadata. The publisher also adds A-Core metadata to the content metadata record for each e-journal article. The following metadata is generated: Dublin Core Content Metadata ============================ Title: Saving the Forests Creator: Nicola Corks Type: Article Contributor: Maddie J (photographer) A-Core Metadata =============== Name: Crystal, Jacky Email: jacky@tree-online.com Contact: Phone 555 11111 Activity: created Date: 1999-01-01 DateRange: 1999-01-01/1999-12-31 Rights: Copyright Trees Journal 1999 A few months later, the Dublin Core content metadata is updated (by a different person from the same publisher) to reflect changes in one of the online articles. The new metadata now contains: Dublin Core Content Metadata ============================ Title: Saving the Forests Creator: Nicola Corks Type: Article Contributor: Maddie J (photographer) Date: 1999-03-09 (modified) A-Core Metadata =============== --------------------------------- Name: Crystal, Jacky Email: jacky@tree-online.com Contact: Phone 555 11111 Activity: created Date: 1999-01-01 --------------------------------- Name: Oldman, Sam Email: sam@tree-online.com Contact: Phone 555 22222 Activity: modified Date: 1999-03-10 --------------------------------- DateRange: 1999-01-01/1999-12-31 Rights: Copyright Trees Journal 1999 5. A-Core Syntax Examples The examples provided in this section are for guidance purposes only. It is advisable to utilise a metadata editor program for the generation of the encodings. 5.1 A-Core Namespace The namespace URI assigned to A-Core described in this document for the purpose of unique identification within various syntax encodings is: http://metadata.net/ac/2.0 In most cases, the A-Core namespace will use the "AC" prefix. 5.2 HTML META Syntax Below is an example of the use of the A-Core metadata elements using the HTML META syntax [6]. The example shows how to encode the second metadata instance from Section 4. ----------------------------------------------------------------------- ----------------------------------------------------------------------- Note: The HTML META encoding does not provide any element grouping mechanism. It is assumed that the order of the elements will be preserved. Systems that support A-Core metadata must ensure and enforce this. 5.3 RDF/XML Syntax Below is an example of the use of the A-Core metadata elements using the RDF/XML syntax [3]. The example shows how to encode the second metadata instance from Section 4. ----------------------------------------------------------------------- Saving the Forests Nicola Corks Article Maddie J (photographer) 1999-03-09 Crystal, Jacky jacky@tree-online.com Phone 555 11111 created 1999-01-01 Oldman, Sam sam@tree-online.com Phone 555 22222 modified 1999-03-10 1999-01-01/1999-12-31 Copyright Trees Journal 1999 ----------------------------------------------------------------------- Note: The RDF/XML encoding does not provide any element grouping mechanism. It is assumed that the order of the elements will be preserved. Systems that support A-Core metadata must ensure and enforce this. 6. Internationalisation All the A-Core elements can be associated with language information using RFC 1766 [8]. The A-Core identifiers are used in the communication of metadata between systems, with human-readable names being available in multiple languages for client systems. 7. Security Considerations The A-Core element set poses no risk to computers and networks. Human clients who obtain metadata that has been incorrectly described (by humans) may face minimal risk in determining the correctness of the metadata. The application of Digital Signature technology is recommended by systems requiring high levels of authentication. 8. Acknowledgements The work reported in this paper has been funded in part by the Cooperative Research Centres Program through the Department of the Prime Minister and Cabinet of Australia and from the National Priority (Reserve) Fund allocation for Improved Library Infrastructure administered by the AV-CC Standing Committee on Information Resources. The authors wish to thank the following for feedback on this document: David Bearman, Simon Cox, Lloyd Sokvitne, Hoylen Sue, and Neil Thompson. 9. References [1] RFC 2413, Dublin Core Metadata for Resource Discovery [2] Education Network Australia (EdNA) Metadata [3] Resource Description Framework (RDF) Model and Syntax [4] Encoding Dublin Core Metadata in HTML [5] ISO 11179 Parts 1-6, Specification and Standardization of Data Elements ftp://sdct-sunsrv1.ncsl.nist.gov/x3l8/11179/ [6] RFC822 Standard for the Format of ARPA Internet Text Messages [7] Date and Time Formats (based on ISO 8601), W3C Technical Note [8] RFC 1766, Tags for the Identification of Languages [9] Australian Government Locator Service (AGLS) Metadata [10] USMARC Relator Code List 10. Authors' Addresses Renato Iannella DSTC Pty Ltd The University of Queensland Qld, 4072, AUSTRALIA Email: renato@dstc.edu.au Voice: +61 7 3365 4310 Fax: +61 7 3365 4311 Debbie Campbell National Library of Australia Canberra ACT, 2600, AUSTRALIA Email: dcampbel@nla.gov.au Voice: +61 2 6262 1673 Fax: +61 2 6273 2545