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Introduction to RDF Paul Miller UK Office for Library & Information Networking Thomas Hofmann Australian Museums On-Line

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Presentation on theme: "Introduction to RDF Paul Miller UK Office for Library & Information Networking Thomas Hofmann Australian Museums On-Line"— Presentation transcript:

1 Introduction to RDF Paul Miller UK Office for Library & Information Networking Thomas Hofmann Australian Museums On-Line (Based closely upon an earlier presentation by Eric Miller of OCLC)

2 Metadata: Definition zTraditionally: ymetadata has been understood as Data about Data zExample(s): ya library catalogue contains information (metadata) about publications (data) ya file system maintains permissions (metadata) about files (data)

3 Metadata: Definition (Cont.) zMetadata describes other data yOne applications metadata is another applications data yMetadata can itself be described by metadata (but that doesnt make it meta- metadata) zExample: yPrice lists (metadata) have expiration dates: metadata about metadata. It is still just metadata.

4 Applications of Metadata zCataloguing (Item and Collections) zResource Discovery zElectronic Commerce zIntelligent Software Agents zDigital Signatures zContent Rating zIntellectual Property Rights zPrivacy Preferences & Policies

5 Application: Item and Collection Cataloguing zDescribing individual resources ydocuments, pages, images, audio files, etc. zDescribing the content of collections: yWeb sites, databases, directories, etc. zRelationships among Resources yTables of Content, chapters, images…. ySite Maps ye.g. CIMI collection records

6 Application: Resource Discovery zSearch engines can better understand the contents of a particular page zMore accurate searches zAdditional information aids precision zMakes it possible to automate searches because less manual weeding is needed to process the search results

7 Application: Electronic Commerce zMetadata can be used to encode information needed in all stages of electronic commerce ylocating seller/buyer & product xsearching yellow pages yagreeing on terms of sale xprices, terms of payment, contractual information ytransactions xdelivery mechanisms, dates, terms

8 Application: Intelligent Agents zrepresentation and sharing of knowledge yknowledge exchange ymodelling zcommunication yuser-to-agent, agent-to-agent, agent-to- service zresource discovery ygives web-roaming agents the ability to understand their environment

9 Application: Digital Signatures zThese are key to building the Web of Trust zRequired by yagents yelectronic commerce ycollaboration zRDF will become the preferred way to encode digital signatures on documents and on statements about documents

10 Application: Content Rating zEmpowering users to select which kinds of web content they wish to see zChild Protection zW3C PICS (Platform for Internet Content Selection) working group yUS Communications Decency Act of 1996 ysimple metadata architecture yprecursor to RDF

11 Other Applications zPrivacy Preferences and Policies ydescribing a users willingness/reluctance to disclose information about himself/herself ydescribing a site administrators desire to gather information about visiting users zIntellectual Property Rights ycontractual terms related to usage and distribution rights to a document

12 Metadata Transmission Embedded (e.g. META) Associated With (in HTTP header) Trusted Third Party (explicit HTTP GET)

13 Metadata Assertions zMetadata requirements will evolve zThe Web is machine-readable but not machine-understandable zMetadata is useful ye.g A lot could be gained from structured description of pages, servers, search services, and other resources zSee point 1

14 Introducing: RDF zImprove on PICS, HTML, and XML zMachine understandable metadata zSupport structured values zSupport metadata bureaux zEncourage authenticated metadata zBase for a variety of descriptions: ycataloging, privacy, accessibility, IPR,...

15 Data Integration zExample: yThe author of a document is Paul yPaul is the author of a document yA document is authored by Paul yThe author of a document is Paul zRepresentation(s) in XML: Paul Paul

16 Data Integration (cont.) zComplexity of querying XML documents yN ways of mapping XML to logical structure yRequires the normalization of all possible representations for effective query zMean the same thing to a person zMean very different things to a machine zRDF much less flexible yless flexible == more interoperable! yconsistent way of representing statements

17 RDF Components zFormal data model zSyntax for interchange of data zSchema Type system (schema model) zSyntax for machine-understandable schemas zQuery and profile protocols

18 RDF Data Model zImposes structural constraints on the expression of application data models y for consistent encoding, exchange and processing of metadata zEnables resource description communities to define their own semantics zProvides for structural interoperability

19 RDF Data Model zDirected labelled graphs zModel elements yResource yProperty yValue yStatement

20 RDF Model Primitives Resource Property Value Resource Statement

21 Simple Example Resource Author Paul

22 RDF Syntax zRDF Model defines a formal relationships among resources, properties and values zSyntax is required to... yStore instances of the model into files yCommunicate files from one application to another zW3C XML eXtensible Markup Language yhttp://www.w3.org/XML

23 RDF Model Example #1 URI:R RDF Presentation Title Creator dc: Paul Miller

24 RDF Syntax Example URI:R RDF Presentation Title Creator dc: Paul Miller

25 Paul Miller URI:PAUL ukoln.ac.uk Paul Miller UKOLN bib: bib:Aff bib:Name RDF Model Example #2 URI:R URI:UKOLN RDF Presentation Title Creator dc:

26

27 Eric Miller RDF Model Example #3 URI:R URI:PAUL ukoln.ac.uk Paul Miller OCLC bib: bib:Aff bib:Name URI:UKOLN RDF Presentation Title Creator admin:By admin:On LOC admin:For... dc:

28 Where do you stop? zModel provides enabling technology zDegree of metadata simplicity/complexity is a matter of: yResource description communities needs, best- practice and experience yOrganization/Institutions Policy yEconomics yGoals and requirements of implementation

29 RDF Schemas zDeclaration of vocabularies yproperties defined by a particular community ycharacteristics of properties and/or constraints on corresponding values zSchema Type System - Basic Types yProperty, Class, SubClassOf, Domain, Range yMinimal (but extensible) at this time yminimize significant clashes with typing system designed for XML NG DTDs (1999?) zExpressible in the RDF model and syntax

30 Schema Vocabularies zEnables communities to share machine readable tokens and locally define human readable labels. dc:Creator Nom rdfs:label Author rdfs:label $100 $a rdfs:label

31 Relationships among vocabularies dc:Creator ms:Kgrip marc:245 bib:Author

32 Relationships among vocabulary elements URI:R John Smith ms:Kgrip dc:Creatorms:Kgrip rdfs: subPropertyOf rdfs:label Key Grip dc:Creator

33 Bringing it together zRDF Metadata transmission yEmbedded (e.g. ), Transmitted with resource (HTTP), Trusted 3rd Party (HTTP GET) zRDF Data Model ySupport consistent encoding, exchange and processing of metadata… critical when aggregating data from multiple sources zRDF Schema yDeclare, define, reuse vocabularies

34 RDF Summary zRDF is a general-purpose framework zRDF provides structured, machine- understandable metadata for the Web zMetadata vocabularies can be developed without central coordination zRDF Schemas describe the meaning of each property name zSigned RDF is the basis for trust

35 RDF Information zW3C RDF Model and Syntax Speciation yRecommendation Status Feb 24, 1999 zW3C RDF Schema Specifications yProposed Recommendation Status Mar 4, 1999 zW3C RDF Home Page yhttp://www.w3.org/RDF/

36 RDF and the Dublin Core zRDF zDublin Core yOverview yData Model yExamples yQualification Mechanisms

37 Dublin Core Data Model zApplication of the RDF Data Model zSufficient richness in RDF to support Dublin Core modelling goals zDefines implementation and extensibility framework for Dublin Core based applications yCIMI is an example of these applications yMICI could be an example of these applications

38 DC Data Model Qualifiers zElement Qualifier (and Terms) zValue Qualifier (and Terms) zValue Types (and Terms) zValue Components zLanguage

39 The Dublin Core Data Model as RDF rdf:Valuedc : Element R dcq:Type (element qualifier) dcq:Scheme (value qualifier)

40 An example for Date Created dcq:DateType rdf:Valuedc:Date Resource ISO 8601 dcq : Scheme

41 An example for Relation R IsPartOf dcq:RelationType dc:Relationrdf:Value

42 Element Qualifier (and Terms) zEnabling mechanisms in the data model that support the qualification of the element relating the resource and the value ye.g. The term Illustrator may be used to qualify the Creator element that relates some resource and some value zTerms yResource identifying Illustrator

43 Value Qualifier (and Terms) zIdentifies the encoding, parsing and/or processing rules associated with a value yLNF: Lastname,[sp]Firstname yISO8601: yDDC: yAAT: ionic column zTerms yResources defining LNF, ISO8601, DDC, AAT, etc.

44 Language zDefines the Language of the value ylang=fr chat vs. lang=en chat zXML provides a way of handling of language (xml:lang) yRDF adopts this, DC adopts this

45 What do you get for this? zThe separation of these constructs is important for extensibility by other resource description communities zDublin Core Metadata Initiative will not define an all inclusive set Terms zIt will define a canonical set and the enabling mechanisms for other communities to extend these

46 RDF Data Model zDesigned to impose structural constraint on syntax to support consistent encoding, exchange and processing of metadata zEnables resource description communities to define their own semantics zProvides for structural interoperability Resource Property Value Resource2

47 Dublin Core Data Model dc:Creator Paul Miller

48 Dublin Core Data Model dc:Creatorrdf:Value Paul Miller

49 Dublin Core Data Model dct:Illustrator dc:Creator dcq: CreatorType rdf:Value Paul Miller

50 Dublin Core Data Model dct:Illustratordct:LNF dc:Creator dcq: AgentType dcq: AgentScheme rdf:Value Miller, Paul

51 Dublin Core Data Model dct:Person dct:LNF dc:Creator dcq: AgentType dcq: AgentScheme rdf:Value Miller, Paul dct:Illustrator rdf:Type

52 Dublin Core Data Model Author dc:Creator dcq:Type rdf:Value 411.org/ pmiller

53 Dublin Core Data Model Author dc:Creator dcq:Type rdf:Value 411.org/ pmiller

54 Dublin Core Data Model dct:Illustrator dcq:CreatorType dc:Creator rdf.411.org/ pmiller

55 Dublin Core Data Model dct:Illustrator dc:Creator dcq:CreatorType rdf.411.org/ pmiller vc:fn vc:mn vc:ln A. Paul Miller

56 Dublin Core Data Model dcq:CreatorType dc:Creator rdf.411.org/ pmiller

57 Dublin Core Data Model dcq:CreatorType Bag cimi:sculptor rdf:Type rdf:_1 rdf:_2 dct:Author dc:Creator rdf.411.org/ pmiller

58 Key Data Model Decisions zApplication of RDF Data Model zDC namespace defines the core elements yhttp://purl.org/dc/elements/1.0/ zDCQ namespace defines the Dublin Core qualifier and extensibility mechanisms yhttp://purl.org/dc/qualifiers/1.0/ zDCT namespace defines the Dublin Core terms and extensibility mechanisms yhttp://purl.org/dc/terms/1.0/

59 Key Data Model Open Issues zThere still a few zDublin Core Data Model Working Draft yout in April yDC Proposed Recommendation shortly after zDublin Core Data Model Home Page yhttp://purl.org/dc/groups/datamodel.htm

60 Additional Information zRDF Home Page yhttp://www.w3.org/RDF zDublin Core Metadata Initiative yhttp://purl.org/dc/


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