RDFSlide 2Slide 3PowerPoint PresentationThe Dublin CoreSlide 6Slide 7Slide 8RDF ContainersSlide 10Slide 11Slide 12Slide 13The Semantic WebSlide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24What is a Resource?Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Internet Technologies 1RDFThese slides were built using modified examples from “XML How To Program” byDeitel, Deitel, Nieto, Lin and Sadhu. The slides also make use of material from “XML Bible” by Elliotte Rusty Harold.In what follows, a “resource” might be a web page, an element in a web page, adevice, a person and more.Internet Technologies 2RDF• The Resource Description Framework (RDF) is a W3C recommendation for an XML encoding of metadata.• A standard for encoding metadata is important for finding and describing resources.• Card catalogs (with wooden drawers and index cards) have been used for years to record metadata about the collection of materials in the library. An RDF document or element makes statements about resources. A statement can be thought of as an ordered triple composed of three items: (resource, property-type, property-value)Internet Technologies 3RDF(resource, property-type, property-value) It is required that each resource have a URI.http://www.andrew.cmu.eduhttp://www.andrew.cmu.edu/~mm6/my.xml#root().child(1)mailto:[email protected]:isbn:0764532367A property is a specific characteristic, attributeor relationship of a resource. Each property has a specific meaningthat can be identified by the property’s name and the associated schema. The schema must actually be pointed to by the property’s namespace.The schema describes the values or value ranges that are permitted for theproperty.Internet Technologies 4<?xml version = "1.0"?><!-- Fig. 22.3 : simple.rdf --><!-- Simple usage of RDF --><rdf:RDF xmlns:rdf = "http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc = "http://purl.org/dc/elements/1.1/"> <rdf:Description about="http://www.deitel.com"> <dc:Title>Deitel and Associates, Inc.</dc:Title> <dc:Description> This is the home page of Deitel and Associates, Inc. </dc:Description> <dc:Date>2000-5-24</dc:Date> <dc:Format>text/html</dc:Format> <dc:Language>en</dc:Language> <dc:Creator>Deitel and Associates</dc:Creator> </rdf:Description></rdf:RDF>The root element of an RDF document is RDF.Each property of the resource being describedis a child element of the Description element.The content of the child is the value of theproperty.Namespaces are used to distinguish betweenRDF elements and elements in property typesand values.Describinga web siteInternet Technologies 5The Dublin CoreA collection of elements designed to provide a similar structure as thatprovided by a card catalog. For example, the following are elements definedin the Dublin Core namespace:TITLE The name given to the resourceCREATOR The person or organization that created …SUBJECT The topic of the resource…DESCRIPTION…:: In the near future, this Dublin Core “schema” is likely to be encoded with a formal syntax.Perhaps this syntax will be RDF.Internet Technologies 6<?xml version = "1.0"?><!-- Fig. 22.3 : simple.rdf --><!-- Simple usage of RDF --><rdf:RDF xmlns:rdf = "http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc = "http://purl.org/dc/elements/1.1/"> <rdf:Description about="http://www.deitel.com"> <dc:Title>Deitel and Associates, Inc.</dc:Title> <dc:Description> This is the home page of Deitel and Associates, Inc. </dc:Description> <dc:Date>2000-5-24</dc:Date> <dc:Format>text/html</dc:Format> <dc:Language>en</dc:Language> <dc:Creator>Deitel and Associates</dc:Creator> </rdf:Description></rdf:RDF>A single RDF element can containany number of Description elements.A Description element can statemore than one property abouta resource. Some properties may be resource valued. For example,suppose Deitel and Associates has an email address…Internet Technologies 7<?xml version = "1.0"?><!-- Fig. 22.3 : simple.rdf --><!-- Simple usage of RDF --><rdf:RDF xmlns:rdf = "http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc = "http://purl.org/dc/elements/1.1/"> <rdf:Description about="http://www.deitel.com"> <dc:Title>Deitel and Associates, Inc.</dc:Title> <dc:Description> This is the home page of Deitel and Associates, Inc. </dc:Description> <dc:Date>2000-5-24</dc:Date> <dc:Format>text/html</dc:Format> <dc:Language>en</dc:Language> <dc:Creator> <rdf:Description about = “mailto:[email protected]” > <dc:Title>Deitel and Associates</dc:Title> </rdf:Description> </dc:Creator> </rdf:Description></rdf:RDF>The Creator becomes a resource rather than a literal. This is a resourcevalued property.Another way to say the samething is with a resourceattribute…Internet Technologies 8<?xml version = "1.0"?><!-- Fig. 22.3 : simple.rdf --><!-- Simple usage of RDF --><rdf:RDF xmlns:rdf = "http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc = "http://purl.org/dc/elements/1.1/"> <rdf:Description about="http://www.deitel.com"> <dc:Title>Deitel and Associates, Inc.</dc:Title> <dc:Description> This is the home page of Deitel and Associates, Inc. </dc:Description> <dc:Date>2000-5-24</dc:Date> <dc:Format>text/html</dc:Format> <dc:Language>en</dc:Language> <dc:Creator rdf:resource = “mailto:[email protected]” /> </rdf:Description> <rdf:Description about = “mailto:[email protected]” > <dc:Title>Deitel and Associates</dc:Title> </rdf:Description> </rdf:RDF>Internet Technologies 9RDF ContainersAn RDF element may describe a resource with multiple properties of the same type.Perhaps a book has several authors or a web page may be found at several sites.RDF defines three types of container objects:Bag – a group of unorderd properties – use li.Seq – a sequence (ordered list) of propertiesAlt – a list of alternative properties from which to choose a single oneLet’s look at a more involved example from Deitel and Deitel…Internet Technologies 10<?xml version = "1.0"?><!-- Fig. 22.5 : links.rdf --><!-- Describing entire Web site --><rdf:RDF xmlns:rdf = "http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc = "http://purl.org/dc/elements/1.1/"><rdf:Description about = "www.deitel.com"> <dc:Title>Home page of Deitel products</dc:Title> <dc:Creator>Deitel