1. Guidance on expressing the Dublin Core within the Resource Description Framework(RDF) Eric Miller, Paul Miller, Dan Brickley Dublin Core Metadata Initiative 元智資工所 系統實驗室 楊錫謦 1999/10/13

2. Outline Introduction A syntax for the Dublin Core Enriching the Dublin Core Examples Conclusion

3. Introduction The Dublin Core Metadata Initiative is a cross- disciplinary international effort to develop mechanisms for the discovery-oriented description of diverse resources. The Dublin Core Element Set comprises 15 elements which together capture a representation of essential aspects related to the description of resources. This document represents a suggested mechanisms by which both simple and complex Dublin Core might be expressed using the XML.

4. A syntax for the Dublin Core 1.Essential elements of an XML-encoded Dublin Core description a. XML version declaration b. Declaring the use of RDF c. Element names should be expressed in lower case. d. XML tags must close.

5. A syntax for the Dublin Core(Cont.) e. XML permits the replacement of with. 2. A useful by-product: xml:lang XML, via the declaration, provides the ability to identify the language in which individual elements of metadata are expressed.

6. A syntax for the Dublin Core(Cont.) 3. Example <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.0/"> Joe Smith

7. A syntax for the Dublin Core(Cont.) 4. Encoding Dublin Core in RDF with HTML <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.0/"> Joe Smith My document --------------------------------------------------------- <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.0/"> <rdf:Description rdf:about="http://doc" dc:creator="Joe Smith" dc:title="My document" />

8. Enriching the Dublin Core 1. Requirements Rather than entering a string of numbers or letters into an element, it is useful to have the ability to identify the coding system utilized. It is perceived as useful to semantically refine some elements which encompass broad concepts or topics. It is frequently important to describe class-type relationships to other concepts or resources. It is necessary for implementors to use additional metadata vocabularies alongside the Dublin Core Element Set in order to meet their local needs. In some cases, users perceive the need to further subdivide and categorize values inserted into Dublin Core elements.

9. Enriching the Dublin Core(Cont.) 2. Qualification Components

10. Enriching the Dublin Core(Cont.) Element Qualifiers: The solution in order to meet the requirement of many implementors to specify aspects of a given resource with greater precision than is offered. Element Qualifier Terms: Element Qualifier Terms represent permissible value for any given Element Qualifier. Value Qualifiers: The solution in order to meet the requirement of many implementors to specify the manner in which a value is encoded. Value Qualifier Terms: Value Qualifier Terms represent permissible value for any given Value Qualifier.

11. Enriching the Dublin Core(Cont.) 3. Repetition or grouping of element or their values is desirable. Bag: Bags are used to declare that a property has multiple values and that the order does not matter. Sequence: Sequence is used to declare that a property has multiple values and that the order of the values is significant. Alternative: A list of resources or literals that represent alternatives for value of a property.

12. Enriching the Dublin Core(Cont.) 4. Managing complexity

13. Examples-1 <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc = "http://purl.org/dc/elements/1.0/" xmlns:dcq = "http://purl.org/dc/qualifiers/1.0/"> Joe Smith Illustrator

14. Examples-2

15. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc = "http://purl.org/dc/elements/1.0/" xmlns:vcard = "http://www.imc.org/vcard/3.0/"> Joe Smith joe@my.com My Company, Inc.

16. Examples-3

17. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc = "http://purl.org/dc/elements/1.0/" xmlns:dcq = "http://purl.org/dc/qualifiers/1.0/" xmlns:vcard = "http://www.imc.org/vcard/3.0/"> <dcq:creatorType rdf:resource = "http://purl.org/dc/terms/1.0/creator/type/ Illustrator"/>

18. Examples-3 Joe Smith joe@my.com My Company, Inc.

19. Conclusion With the increasing availability of electronic information in a plethora of forms, the need for an effective means by which these resources might be described grows ever greater. Existing mechanisms to describe particular forms of resource within individual communities continue to improve, but the need is most pressing between and across communities.