1. Resource Description Framework ( RDF ) Xinxia An

2. Resource Description Framework ( RDF )  Introduction  RDF Syntax  Dublin Core

3. What is RDF ?  RDF: Resource Description Framework  Is a language designed to describe resources which has its own formal grammar which has its own formal grammar  Is a framework: tells us how to organize metadata tells us how to organize metadata does not say what metadata we should have does not say what metadata we should have  Is an XML application  Is a W3C recommendation Introduction

4. What is Dublin Core ?  Is a metadata standard  Tells us what aspects of a resource we should describe and what names to useIntroduction

5. Why need RDF and Dublin Core ?  Provides a foundation for metadata processing  Supports metadata interchanging  better precision in resource discovery Introduction

6. (Root Element)  A RDF document must start with declaration  It also must have a root element with a fixed name which is  It also must have a root element with a fixed name which is  It must use the RDF namespace, which is http://www.w3.org/1999/02/22-rdf-syntax-ns# http://www.w3.org/1999/02/22-rdf-syntax-ns#http://www.w3.org/1999/02/22-rdf-syntax-ns#  The prefix for this namespace is usually rdf RDF Syntax

7. Root Element <rdf:RDF <rdf:RDF xmlns:rdf=“http://www.w3.org/ xmlns:rdf=“http://www.w3.org/ 1999/02/22-rdf-syntax-ns#”> 1999/02/22-rdf-syntax-ns#”>. Description Elements ( Description Elements ). RDF Syntax

8. Description Element  Each resource you want to describe in RDF document gets its own element  We use about attribute to specify the resource to be described RDF Syntax

9. Description Element <rdf:RDF <rdf:RDF xmlns:rdf=“http://www.w3.org/ xmlns:rdf=“http://www.w3.org/ 1999/02/22-rdf-syntax-ns#”> 1999/02/22-rdf-syntax-ns#”> <rdf:Description <rdf:Description about=“”> about=“http://www.nmsu.edu/jobs.html”>http://www.nmsu.edu/jobs.html …… …… ( Property Elements ) ( Property Elements ) …… …… </rdf:RDF> RDF Syntax

10. Description Element  attributes of element about about aboutEach aboutEach aboutEachPrefix aboutEachPrefix bagID bagID ID ID type type RDF Syntax

11. Property Element  Each property element describes one property or one aspect of the resource or one aspect of the resource  It is up to you to decide how to name the properties properties  But it is strongly suggested to use agreed-upon sets of terms sets of terms  The most widely used standard is Dublin Core whose namespace is usually given a prefix dc whose namespace is usually given a prefix dc http://www.purl.org/DC/ http://www.purl.org/DC/http://www.purl.org/DC/ RDF Syntax

12. Property Element  Some forms of property elements 1. Value Value = string | Description | Container e.g.1 John Smith e.g.1 John Smith e.g.2 e.g.2 en en Feb.18,2002 Feb.18,2002 RDF Syntax

13. Property Element  Some forms of property elements 2. any well-formed XML (not interpreted by RDF-aware browers) e.g. John Smith John Smith Jan 01,1900 Jan 01,1900 RDF Syntax

14. Property Element  Some forms of property elements 3. property elements e.g. John Smith John Smith Jan 01,1900 Jan 01,1900 RDF Syntax

15. Property Element  Some forms of property elements 4. URI = Uniform Resource Identifiere.g. <rdf:Description <rdf:Description about=“”> about=“http://nmsu.edu/jobs.html”>http://nmsu.edu/jobs.html smith.html RDF Syntax

16. RDF Document - Example <rdf:RDF xmlns:rdf=“http://www.w3.org/ xmlns:rdf=“http://www.w3.org/ 1999/02/22-rdf-syntax-ns#” 1999/02/22-rdf-syntax-ns#” xmlns:dc=“http://purl.org/DC/”> xmlns:dc=“http://purl.org/DC/”>http://purl.org/DC/ <rdf:Description <rdf:Description about=“”> about=“http://www.nmsu.edu/jobs.html”>http://www.nmsu.edu/jobs.html John Smith John Smith Feb.18,2002 Feb.18,2002 </rdf:RDF> RDF Syntax

17. Abbreviated RDF Syntax Abbreviated RDF Syntax  Up to now, we place all the property elements inside the description elements  W3C also provides another way to organize the property elements, which is called abbreviated RDF syntax  Abbreviated RDF syntax allows us convert property elements into attributes of the element RDF Syntax

18. Abbreviated RDF Syntax John Smith Feb 18, 2002 is converted into <rdf:/Description about=“jobs.html” dc:Creator=“ John Smith “ dc:Date=“ Feb 18, 2002 ”> RDF Syntax

19. Abbreviated RDF Syntax  Abbreviate RDF syntax results in empty description elements  The biggest advantage of this is that browsers that do not understand RDF, will not mishandle the content of the property elements, if we embed some RDF descriptions in an HTML document RDF Syntax

20. RDF Containers  A RDF container is a group of properties of a resource of a resource  With RDF containers, we could describe a resource more conveniently and efficiently RDF Syntax

21. RDF Containers  Without RDF container, we have to repeat the property tags like Mercury Mercury Venus Venus Earth Earth Mars Mars </rdf:Description> if Mercury, Venus, Earth and Mars are all subjects of the resource planets.html if Mercury, Venus, Earth and Mars are all subjects of the resource planets.html RDF Syntax

22. RDF Containers There are three types of RDF containers a group of multiple,unordered properties a group of multiple,unordered properties a group of multiple,ordered properties a group of multiple,ordered properties a list of properties giving alternative choices, a list of properties giving alternative choices, only one of all these choices is actually chosen only one of all these choices is actually chosen RDF Syntax

23. RDF Containers - Bag John Smith John Smith Mercury Mercury Venus Venus Earth Earth Mars Mars </rdf:Description> RDF Syntax

24. RDF Containers - Seq John Smith John Smith Mercury Mercury Venus Venus Earth Earth Mars Mars </rdf:Description> RDF Syntax

25. Why Dublin Core ?  RDF is just a framework under which we organize our metadata about resources  It does not say anything about what properties or aspects of a resource we should describe  We need some standard property names or agreed-upon terms to describe resources, otherwise, the metadata is not easy to share or exchange  Dublin Core comes for this reason Dublin Core

26. What is Dublin Core ?  Is a metadata standard  Is a set of named properties  Is a description model  Tells us what aspects of a resource should be described  Is the most popular and supported by most search engines Dublin Core

27. Dublin Core Properties The Dublin Core standard has 15 properties of 3 categories Content Intellectual Property Instantiation Dublin Core

28. Content Properties Coverage Description Type Relation Source Subject Title Dublin Core

29. Type Property text image sound software... Dublin Core

30. Intellectual Properties Contributor Creator Publisher Rights Dublin Core

31. Instantiation Properties Date Format Identifier Language Dublin Core

32. Summary  RDF is a language about how to write RDF documents  RDF does not specify what properties or aspects of a resource we should describe  Dublin Core provides a standard way to describe resources by giving a set of agreed-upon terms