Internet Technologies1 RDF Bibliography: “XML How To Program” by Deitel, Deitel, Nieto, Lin and Sadhu. “XML Bible” by Elliotte Rusty Harold. HP’s Jena.

Internet Technologies 1

RDF

Bibliography:“XML How To Program” by Deitel, Deitel, Nieto, Lin and Sadhu. “XML Bible” by Elliotte Rusty Harold.HP’s Jena Tutorial.

The Resource Description Framework


Some notes on RDF 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. A “resource” is anything with a URI. This would include people, books, devices and so on.

Card catalogs, for example, have been used for years to record metadata about the collection of materials in libraries. Is Google the card catalogue for the web? Are we done?

All OWL documents are RDF documents. All RDF documents are OWL Full documents.


Some Notes On RDF(2)

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)


Some Notes on RDF(3)

(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:0764532367

A 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.


<?xml version = "1.0"?>



<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 site


The 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…::





<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…





<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…





<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>


RDF Containers

An 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 one

Let’s look at a more involved example from Deitel and Deitel…






<rdf:Description about = "www.deitel.com"> <dc:Title>Home page of Deitel products</dc:Title> <dc:Creator>Deitel and Associates, Inc.</dc:Creator> <dc:Subject> <rdf:Bag ID = "links_1"> <rdf:li resource = "http://www.deitel.com/books/index.htm"/> <rdf:li resource = "http://www.deitel.com/services/training/index.htm"/> </rdf:Bag>

Statements can be made about a container as a whole and so we givethe container an ID.


<rdf:Bag ID = "links_2"> <rdf:li resource ="http://www.deitel.com/announcements/contractors.htm"/> <rdf:li resource ="http://www.deitel.com/announcements/internships.htm"/> </rdf:Bag>

<rdf:Seq ID = "links_3"> <rdf:li resource = "http://www.deitel.com/intro.htm"/> <rdf:li resource = "http://www.deitel.com/directions.htm"/> </rdf:Seq> </dc:Subject></rdf:Description>

<rdf:Description aboutEach = "#links_1"> <dc:Description>About our Products</dc:Description></rdf:Description>

The aboutEach attributeapplies to each element in thecontainer.


<rdf:Description aboutEach = "#links_2"> <dc:Description> Announcements, Oppurtunities and internships at Deitel Associates </dc:Description></rdf:Description>

<rdf:Description aboutEach = "#links_3"> <dc:Description>All about us</dc:Description></rdf:Description>

<rdf:Description about = "http://www.deitel.com/books/index.htm">  <rdf:Title> Books, Multimedia Cyber Classrooms and Complete Training Courses </rdf:Title></rdf:Description>

<rdf:Description about = "http://www.deitel.com/services/training/index.htm"> <rdf:Title>Corporate Training Courses</rdf:Title></rdf:Description>


<rdf:Description about = "http://www.deitel.com/announcements/contractors.htm"> <rdf:Title>Looking for Training Contractors</rdf:Title></rdf:Description>

<rdf:Description about = "http://www.deitel.com/announcements/internships.htm"> <rdf:Title> Internships at Deitel and Associates, Inc. </rdf:Title></rdf:Description>

<rdf:Description about = "http://www.deitel.com/intro.htm"> <rdf:Title> Introduction to Deitel and Associates, Inc. </rdf:Title></rdf:Description>

<rdf:Description about = "http://www.deitel.com/directions.htm"> <rdf:Title>Our location and how to get there</rdf:Title></rdf:Description> </rdf:RDF>


An RDF Application CC/PP

• The CC/PP working group was formed in August 1999.

• Its mission is to develop an RDF-based framework forthe management of device profile information.


A composite capability/preference profile is a collection of information which describes the capabilities,hardware, system software and applications used by someone accessing the web. Information mightinclude:

• Preferred language (Spanish, French, etc.)• Sound (on/off)• Images (on/off)• Class of device (phone, PC, printer, etc.)• Screen size• Available bandwidth• Version of HTML supported, and so on.

An RDF Application CC/PP


Composite Capability/Preference Profiles (CC/PP)DEVICE PROFILE

CC/PP

RDF

XML

CC/PP provides the equivalentof database fields and associatedmodel for formalizing the device profiles

RDF is language which providesa standard way for using XML torepresent metadata in the form ofproperties and relationships ofitems on the Web.

The device profile and user preferences might be stored in aCC/PP repository. CC/PP is in turn an RDF application.


• The location of the device profile is sent with a request for a Web page.• The CC/PP data is accessed and on the basis of the profile, a Web server can choose the right content. This might be a certain XHTML file or perhaps a suitable document would be generated on the fly.• A document on the server may refer to its own document profile-describing the required capabilities of its client.• The server might match and send or generate and send.

Composite Capability/Preference Profiles (CC/PP)


Each variant of the document has adocument profile describing the browsersupport it needs to display it

DEVICE PROFILESDOCUMENT PROFILES

NEGOTIATE CORRECTCONTENT FOR DEVICES

If none of the document variants are suitable,existing document may be transformed by stylesheet or tool for the purpose, or new documentgenerated

DEVICES RECEIVE RIGHT MARK-UP


More Notes on RDF

The RDF data model is that of a directed edge labeled graph. Nodes are called resources and edge labels are called properties. RDF’s syntax is a convention for representing this model in XML.


person

name

age

email

Alan 42 [email protected] This element describes aresource. We aredescribing two resourcesin this document withunique ID’s.

<rdf:description ID=“001”><person> <rdf.description ID=“002”>

<name>Alan</name><age>42</age><email>[email protected]</email>

</rdf.description></person>

</rdf:description>

An edge in RDF is called a statement.

Four statements have been made.1) resource 001 has property person whose value is resource 002.2) resource 002 has property name with value Alan.3) resource 002 has property age with value 42.4) resource 002 has property email with value [email protected].


Resource1

Resource2

Resource3

PropertyType1 PropertyType3

PropertyType 2 PropertyType 4

“Atomic Value” “Atomic Value”

RDF Data Model


Document 1Author

Resource /Property /Value

Author_001

Affiliation

Name

Email

“Home, Inc.”

“John Smith”

“[email protected]”


Processing RDF in Java

• DOM?

• SAX?

• Jena from HP Research provides another

approach


Jena Example 1

// Modified from HP's Jena Tutorial

import com.hp.hpl.jena.rdf.model.*;import com.hp.hpl.jena.vocabulary.*;

public class Tutorial01 extends Object {

// some definitions

static String personURI = "http://somewhere/JohnSmith";

static String fullName = "John Smith";


public static void main (String args[]) {

// create an empty model (An empty RDF graph)

Model model = ModelFactory.createDefaultModel();

// create the resource

Resource johnSmith = model.createResource(personURI);

// add the property

johnSmith.addProperty(VCARD.FN, fullName);

model.write(System.out);

}

}


D:\McCarthy\www\95-733\examples\Jena>java Tutorial01

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:vcard="http://www.w3.org/2001/vcard-rdf/3.0#" > <rdf:Description rdf:about="http://somewhere/JohnSmith"> <vcard:FN>John Smith</vcard:FN> </rdf:Description>

</rdf:RDF>


A Resource Valued Predicate

// Modified from HP's Jena Tutorial

import com.hp.hpl.jena.rdf.model.*;import com.hp.hpl.jena.vocabulary.*;

public class Tutorial03 extends Object {

public static void main (String args[]) {

String personURI = "http://somewhere/JohnSmith"; String givenName = "John"; String familyName = "Smith"; String fullName = givenName + " " + familyName; // create an empty model Model model = ModelFactory.createDefaultModel();


// create the resource // and add the properties cascading style Resource johnSmith = model.createResource(personURI) .addProperty(VCARD.FN, fullName) .addProperty(VCARD.N, model.createResource() .addProperty(VCARD.Given, givenName) .addProperty(VCARD.Family, familyName));


// list the statements in the graph StmtIterator iter = model.listStatements(); // print out the predicate, subject and object of each statement while (iter.hasNext()) {

Statement stmt = iter.nextStatement(); // get next statement Resource subject = stmt.getSubject(); // get the subject Property predicate = stmt.getPredicate(); // get the predicate RDFNode object = stmt.getObject(); // get the object

System.out.print(subject.toString()); System.out.print(" " + predicate.toString() + " ");


if (object instanceof Resource) {

System.out.print(object.toString());

} else {

// object is a literal

System.out.print(" \"" + object.toString() + "\"");

} System.out.println(" ."); } // end while System.out.println("==================="); model.write(System.out); }}


D:\McCarthy\www\95-733\examples\Jena>java Tutorial0316fa474:fd074695f6:-8000 http://www.w3.org/2001/vcard-rdf/3.0#Given "John" .http://somewhere/JohnSmith http://www.w3.org/2001/vcard-rdf/3.0#FN "John Smith" .16fa474:fd074695f6:-8000 http://www.w3.org/2001/vcard-rdf/3.0#Family "Smith" .http://somewhere/JohnSmith http://www.w3.org/2001/vcard-rdf/3.0#N 16fa474:fd074695f6:-8000 .===================<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:vcard="http://www.w3.org/2001/vcard-rdf/3.0#" > <rdf:Description rdf:nodeID="A0"> <vcard:Given>John</vcard:Given> <vcard:Family>Smith</vcard:Family> </rdf:Description> <rdf:Description rdf:about="http://somewhere/JohnSmith"> <vcard:FN>John Smith</vcard:FN> <vcard:N rdf:nodeID="A0"/> </rdf:Description></rdf:RDF>


Reading OWL with Jena

import com.hp.hpl.jena.rdf.model.*;import com.hp.hpl.jena.ontology.*;

import java.io.*;import java.net.*;

public class ReadWineOntology extends Object { public static void main (String args[]) throws Exception {

// create an empty model

OntModel model = ModelFactory.createOntologyModel();


// read the wine.xml file either way

model.read("file:D:/McCarthy/www/95-733/examples/Jena/wine.xml"); //model.read("http://www.andrew.cmu.edu/user/mm6/ontology/wine.xml");

// write it to standard out

model.write(System.out);

}

}The next step is to use Jena to make or verify deductions.


The Semantic Web

By augmenting web pages with data directed at computers and by adding documents solely for computers, we will transform the web into the Semantic Web.

Intuitive software will be developed that will allow anyone to create Semantic Web Pages.

For the semantic web to function, computers must have access to structured collectionsof information and sets of inference rules that can be used to conduct automated reasoning.

XML has no built-in mechanism to convey the meaning of the user’s new tags to otherusers.

These notes are from an article entitled “The Semantic Web” by Tim Berners-Lee,James Hendler and Ora Lassila appearing in Scientific American, May 2001


The Semantic WebThe challenge of the Semantic Web is to provide a language that expresses bothdata and rules for reasoning about the data and that allows rules from an existing knowledge-representation system to be exported unto the Web.

Ontologies: Collections of statements written in a language such as RDF that definethe relations between concepts and specify logical rules for reasoning about them.

Computers will “understand” the meaning of semantic data on a web page byfollowing links to specified ontologies.

Consider the statement “a hex-head bolt is a type of machine bolt”. We could encode thisin RDF.

When writing code against traditional XML data, the programmer must know what thethe document author uses each tag for.

Meaning is expressed by RDF, which encodes it in a set of triples.


The Semantic WebAn RDF document makes assertions that particular things (people, web pages,or whatever) have properties (such as “is sister of”, “is the author of”) with certain values (another person, another Web page).

We can remove ambiguity by associating each of the three parts with a URI. Forexample:

“(filed 5 in database A) (is a field of type) (zip code)” could be replaced with three URI’s.

An ontology is a document or file that formally defines the relations among terms.

An ontology may express a rule “If a city code is associated with a state code, andan address uses that city code, then that address has the associated state code.”

A program can then draw conclusions.

The meaning of terms or XML codes can be defined by pointers from the page toan ontology.


The Semantic Web

Many automated web based services already exist without semantics, but other programssuch as agents have no way to locate one that will perform a specific function.

Service Discovery will happen only when there is a common language to describe aservice in a way that lets other agents “understand” both the function offered and how to take advantage of it.

Services can advertise their functions in directories analogous to the Yellow Pages.

Devices can advertise their abilities with RDF.

Internet Technologies1 RDF Bibliography: “XML How To Program” by Deitel, Deitel, Nieto, Lin and Sadhu. “XML Bible” by Elliotte Rusty Harold. HP’s Jena.

Documents

rdf elements

propertyvalue slide

rdf documents

internet technologies5

property types

single rdf element

texthtml en deitel

home page of deitel