internet technologies

+

95-733 Internet Technologies

Internet Technologies

The Semantic Web and The Resource Description Framework

(RDF and RDFa)

+

RDF and RDFa

Notes from three articles on course schedule: “What is RDF” by Tim Bray and Joshua Tauberer, the “RDFa Primer” from W3C and from Google’s adoption of RDFa and Microformats.


+ First: Let’s get some RDF

curl --include --location –header "Accept:application/rdf+xml" http://dbpedia.org/resource/Yukihiro_Matsumoto

Can we learn anything from the result?

Is there any other data we can learn from?


+

95-733 Internet Technologies See www.linkeddata.org

Each of these stores many many RDF triples.

+ So, what’s a “triple”?

A triple is a statement in some RDF format.

The next slides shows how we can combine some triples into

Knowledge Graph.


+A Knowledge Graph


+Triples


Start Node Edge Label End Node

vincent_donofrio starred_in law_&_order_cilaw_&_order_ci is_a tv_showthe_thirteenth_floor similar_plot_as the_matrix

+Notation 3 (N3) or Turtle Format

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

@prefix ex: <http://www.example.org/> .

ex:vincent_donofrio ex:starred_in ex:law_and_order_ci .

ex:law_and_order_ci rdf:type ex:tv_show .

ex:the_thirteenth_floor ex:similar_plot_as ex:the_matrix .


+RDF/XML

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"

xmlns:ex="http://www.example.org/">

<rdf:Description rdf:about="http://www.example.org/vincent_donofrio">

<ex:starred_in>

<ex:tv_show rdf:about="http://www.example.org/law_and_order_ci" />

</ex:starred_in>

</rdf:Description>

<rdf:Description rdf:about="http://www.example.org/the_thirteenth_floor">

<ex:similar_plot_as rdf:resource="http://www.example.org/the_matrix" />

</rdf:Description>

</rdf:RDF>


+Another RDF/XML

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"

xmlns:dc="http://purl.org/dc/elements/1.1/"

xmlns:geo="http://www. w3.org/2003/01/geo/wgs84_pos#"

xmlns:edu="http://www.example.org/">

<rdf:Description rdf:about="http://www.princeton.edu">

<geo:lat>40.35</geo:lat>

<geo:long>-74.66</geo:long>

<edu:hasDept rdf:resource="http://www.cs.princeton.edu"

dc:title="Department of Computer Science"/>

</rdf:Description>

</rdf:RDF>


+As A Table

Subject Predicate Object

----------------------------- ----------- --------

<http://www.princeton.edu> edu:hasDept <http://www.cs.princeton.edu>

<http://www.princeton.edu> geo:lat "40.35"

<http://www.princeton.edu> geo:long "-74.66"

<http://www.cs.princeton.edu> dc:title "Department of Computer Science"


+Notation 3

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

@prefix dc: <http://purl.org/dc/elements/1.1/> .

@prefix geo: <http://www. w3.org/2003/01/geo/wgs84_pos#> .

@prefix edu: <http://www.example.org/> .

<http://www.princeton.edu> geo:lat "40.35" ; geo:long "-74.66" .

<http://www.cs.princeton.edu> dc:title "Department of Computer Science" .

<http://www.princeton.edu> edu:hasDept <http://www.cs.princeton.edu> .


+ RDFa and RDF

RDFa is a lightweight version of RDF for web pages.

RDF stands on its own.

We’ll first look at RDFa and then RDF.

RDFa is being used today by search engines like Google and

sites like Best Buy.


+From the RDFa W3C Primer


“When web data meant for humans is augmented with hintsmeant for computer programs, these programs become significantly more helpful.”

+XHTML Without and With RDFa

All content on this site is licensed under

<a href="http://creativecommons.org/licenses/by/3.0/">

a Creative Commons License

</a>

All content on this site is licensed under

<a rel="license" href="http://creativecommons.org/licenses/by/3.0/">

a Creative Commons License

</a>.


The rel, in a link, describesthe relationship between the current pageand the linked page.

+A Link with a Flavor


+Labeling Title and Author


<div> <h2>The trouble with Bob</h2> <h3>Alice</h3> ...</div>

<div xmlns:dc="http://purl.org/dc/elements/1.1/"> <h2 property="dc:title">The trouble with Bob</h2> <h3 property="dc:creator">Alice</h3> ...</div>

RDFa introduces theproperty attribute.

What kind of title? Atitle of a person or a title to land or a title of a work?

+ In RDFa, all property names are, in fact, URLs.


+Multiple Items Per Page


<div xmlns:dc="http://purl.org/dc/elements/1.1/">

<div about="/alice/posts/trouble_with_bob"> <h2 property="dc:title">The trouble with Bob</h2> <h3 property="dc:creator">Alice</h3> ... </div>

<div about="/alice/posts/jos_barbecue"> <h2 property="dc:title">Jo's Barbecue</h2> <h3 property="dc:creator">Eve</h3> ... </div></div>

RDFa provides @about, an attribute for specifying the exact URL to which the contained RDFa markup applies

+As a Diagram


+Alice Gives Bob Credit


<div about="/alice/posts/trouble_with_bob"> <h2 property="dc:title">The trouble with Bob</h2> The trouble with Bob is that he takes much better photos than I do:

<div about="http://example.com/bob/photos/sunset.jpg"> <img src="http://example.com/bob/photos/sunset.jpg" /> <span property="dc:title">Beautiful Sunset</span> by <span property="dc:creator">Bob</span>. </div> </div>

The inner aboutoverrides the outer about.

+As A Graph


+Blog Contact Info


<div> <p> Alice Birpemswick </p> <p> Email: <a href="mailto:[email protected]">[email protected]</a> </p> <p> Phone: <a href="tel:+1-617-555-7332">+1 617.555.7332</a> </p></div> This is mainly useful

for viewing.

+Blog w/FOAF Contact Info


<div typeof="foaf:Person" xmlns:foaf="http://xmlns.com/foaf/0.1/">

<p property="foaf:name">Alice Birpemswick</p> <p>Email: <a rel="foaf:mbox" href="mailto:[email protected]">

[email protected]</a> </p> <p> Phone: <a rel="foaf:phone" href="tel:+1-617-555-7332">+1 617.555.7332</a> </p></div>

The Dublin core has no vocabulary fordescribing friendships.But foaf does.

The typeof is an RDFa attribute that is specifically meant to declare a new data item with a certain type.

+As A Graph


Alice didn't specify @about like she did when adding blog entry metadata. What is she associating these properties with, then? In fact, the @typeof on the enclosing div implicitly sets the subject of the properties marked up within that div. The name, email address, and phone number are associated with a new node of type foaf:Person. This node has no URL to identify it, so it is called a blank node.

+Social Networks


<div> <ul> <li> <a href="http://example.com/bob/">Bob</a> </li> <li> <a href="http://example.com/eve/">Eve</a> </li> <li> <a href="http://example.com/manu/">Manu</a> </li> </ul></div>

These people are allfriends of Alice and she Includes them in her normal HTML blog.

+Adding RDFa


<div xmlns:foaf="http://xmlns.com/foaf/0.1/"> <ul> <li typeof="foaf:Person"> <a href="http://example.com/bob/">Bob</a> </li> <li typeof="foaf:Person"> <a href="http://example.com/eve/">Eve</a> </li> <li typeof="foaf:Person"> <a href="http://example.com/manu/">Manu</a> </li> </ul></div>

First,describethese as Persons.

+Add Homepages


<div xmlns:foaf="http://xmlns.com/foaf/0.1/"> <ul> <li typeof="foaf:Person"> <a rel="foaf:homepage" href="http://example.com/bob/">Bob</a> </li> <li typeof="foaf:Person"> <a rel="foaf:homepage" href="http://example.com/eve/">Eve</a> </li> <li typeof="foaf:Person"> <a rel="foaf:homepage" href="http://example.com/manu/">Manu</a> </li> </ul></div>

Use rel for the linkrelationships.

+Describe Text as Names


<div xmlns:foaf="http://xmlns.com/foaf/0.1/"> <ul> <li typeof="foaf:Person"> <a property="foaf:name" rel="foaf:homepage" href="http://example.com/bob/">Bob</a> </li> <li typeof="foaf:Person"> <a property="foaf:name" rel="foaf:homepage" href="http://example.com/eve/">Eve</a> </li> <li typeof="foaf:Person"> <a property="foaf:name" rel="foaf:homepage" href="http://example.com/manu/">Manu</a> </li> </ul></div>

+Claim in Primer


“Alice is ecstatic that, with so little additional markup, she's able to fully express both a pleasant human-readable page and a machine-readable dataset.”

+Using foaf:knows


<div xmlns:foaf="http://xmlns.com/foaf/0.1/" about="#me" rel="foaf:knows"> <ul> <li typeof="foaf:Person"> <a property="foaf:name" rel="foaf:homepage" href="http://example.com/bob">Bob</a> </li> <li typeof="foaf:Person"> <a property="foaf:name" rel="foaf:homepage" href="http://example.com/eve">Eve</a> </li> <li typeof="foaf:Person"> <a property="foaf:name" rel="foaf:homepage" href="http://example.com/manu">Manu</a> </li> </ul></div> Alice knows these people with these

names and homepages.

+


+Building Custom Vocabularies


1. Selecting a URL where the vocabulary will reside, e.g. http://example.com/photos/vocab#.

2. Distributing an RDF document, at that URL, which defines the classes and properties that make up the vocabulary. For example, Alice may want to define classes Photo and Camera, as well as the property takenWith that relates a photo to the camera with which it was taken.

3. Using the vocabulary in XHTML+RDFa with the usual prefix declaration mechanism, e.g. xmlns:photo="http://example.com/photos/vocab#", and typeof="photo:Camera".

+Microformats Compete with RDFa


hCard Business card data XFN Friends and contacts hCalendar Events hReview Review movies, books, etc..

“When web data meant for humans is augmented with hints meant for computer programs, these programs become significantly more helpful.”

Not from a standards body. A grassroots effort since 2004.

+Microformats Compete with RDFa


As an exercise, visit:

http://microformats.org and build an hCard and an hCalendar.

Use hCard creator and hCalendar creator.

Quiz. What information is requested by the XFN tool?

+Google adopted Microformats and RDFa in 2009


Why? In support of “Rich Snippits”.

See the Rich Snippit Testing Tool at :http://www.google.com/webmasters/tools/richsnippets

“Google Rich Snippets provides structured data in Google search result snippets. Webmasters can provide this structured data by using microformats or RDFa to mark up their web pages. “

+Rich Snippits


“This kind of markup is designed for sites containing specific types of structured data. Google currently supports the following information types: reviews, people profiles, business listings, and events.”

From: http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=99170

+Examples from Google – A Review of a Pizza Joint


The old way:

<div> L’Amourita Pizza Reviewed by Ulysses Grant on Jan 6. Delicious, tasty pizza on Eastlake! L'Amourita serves up traditional wood-fired Neapolitan-style pizza, brought to your table promptly and without fuss. An ideal neighborhood pizza joint. Rating: 4.5 </div> :



With RDFa:

<div xmlns:v="http://rdf.data-vocabulary.org/#" typeof="v:Review"> <span property="v:itemreviewed">L’Amourita Pizza</span> Reviewed by <span property="v:reviewer">Ulysses Grant</span> on <span property="v:dtreviewed" content="2009-01-06">Jan 6</span>. <span property="v:summary">Delicious, tasty pizza on Eastlake!</span> <span property="v:description">L'Amourita serves up traditional wood-fired Neapolitan-style pizza, brought to your table promptly and without fuss. An ideal neighborhood pizza joint. </span> Rating: <span property="v:rating">4.5</span> </div>

Be sure to visit:http://rdf.data-vocabulary.org/rdf.xml



With Microformats:

<div class="hreview"> <span class="item"> <span class="fn">L’Amourita Pizza</span> </span> Reviewed by <span class="reviewer">Ulysses Grant</span> on <span class="dtreviewed"> Jan 6<span class="value-title" title="2009-01-06"> </span> <span class="summary">Delicious, tasty pizza on Eastlake!</span> <span class="description">L'Amourita serves up traditional wood-fired Neapolitan-style pizza, brought to your table promptly and without fuss. An ideal neighborhood pizza joint. </span> Rating: <span class="rating">4.5</span> </div>

+Examples from Google – People


The old way:

<div> My name is Bob Smith, but people call me Smithy. Here is my home page: <a href="http://www.example.com">www.example.com</a>. I live in Albuquerque, NM and work as an engineer at ACME Corp. My friends: <a href="http://darryl-blog.example.com">Darryl</a>, <a href="http://edna-blog.example.com">Edna</a> </div>



In RDFa:

<div xmlns:v="http://rdf.data-vocabulary.org/#" typeof="v:Person"> My name is <span property="v:name">Bob Smith</span>, but people call me <span property="v:nickname">Smithy</span>. Here is my homepage: <a href=http://www.example.com rel="v:url"> www.example.com</a>. I live in <span rel="v:address"> <span typeof="v:Address"> <span property="v:locality">Albuquerque</span>, <span property="v:region">NM</span> </span> </span> and work as an <span property="v:title">engineer</span> at <span property="v:affiliation">ACME Corp</span>. My friends: <a href="http://darryl-blog.example.com" rel="v:friend">Darryl</a>, <a href="http://edna-blog.example.com" rel="v:friend">Edna</a> </div>



In Microformats:

<div class="vcard"> My name is <span class="fn">Bob Smith</span>, but people call me <span class="nickname">Smithy</span>. Here is my home page: <a href=http://www.example.com class="url">www.example.com</a>. I live in <span class="adr"> <span class="locality">Albuquerque</span>, <span class="region">NM</span> </span> and work as an <span class="title">engineer</span> at <span class="org">ACME Corp</span>. My friends: <a href=http://darryl-blog.example.com rel="friend">Darryl</a>, <a href="http://edna-blog.example.com" rel="friend">Edna</a> </div>

+Examples from Google – Events


The old way:

<div> <a href="http://www.example.com/events/spinaltap">Spinal Tap</a> <img src="spinal_tap.jpg" /> After their highly-publicized search for a new drummer, Spinal Tap kicks off their latest comeback tour with a San Francisco show. When: Oct 15, 7:00PM—9:00PM Where: Warfield Theatre, 982 Market St, San Francisco, CA Category: Concert </div>



In RDFa:

<div xmlns:v="http://rdf.data-vocabulary.org/#" typeof="v:Event"> <a href="http://www.example.com/events/spinaltap" rel="v:url" property="v:summary"> Spinal Tap</a> <img src="spinal_tap.jpg" rel="v:photo" /> <span property="v:description">After their highly-publicized search for a new drummer, Spinal Tap kicks off their latest comeback tour with a San Francisco show. </span> When: <span property="v:startDate" content="2009-10-15T19:00-08:00">Oct 15, 7:00PM</span> <span property="v:endDate" content="2009-10-15T21:00-08:00">9:00PM</span> Where: <span rel="v:location"> <span typeof="v:Organization"> <span property="v:name">Warfield Theatre</span>,



<span rel="v:address"> <span typeof="v:Address"> <span property="v:street-address">982 Market St</span>, <span property="v:locality">San Francisco</span>, <span property="v:region">CA</span> </span> </span> <span rel="v:geo"> <span typeof="v:Geo"> <span property="v:latitude" content="37.774929" ></span> <span property="v:longitude" content="-122.419416" ></span> </span> </span></span></span> Category: <span property="v:eventType">Concert</span> </div>



In Microformat:

<div class="vevent"> <a href="http://www.example.com/events/spinaltap" class="url summary">Spinal Tap</a> <img src="spinal_tap.jpg" class="photo" /> <span class="description">After their highly-publicized search for a new drummer, Spinal Tap kicks off their latest comeback tour with a San Francisco show.</span> When: <span class="dtstart"> Oct 15, 7:00PM<span class="value-title" title="2009-10-15T19:00-08:00"></span> </span><span class="dtend"> 9:00PM<span class="value-title" title="2009-10-15T21:00-08:00"></span> </span> Where: <div class="location vcard"> <span class="fn org">Warfield Theatre</span>, <span class="adr"> <span class="street-address">982 Market St</span>, <span class="locality">San Francisco</span>, <span class="region">CA</span> </span>



<span class="geo"> <span class="latitude"> <span class="value-title" title="37.774929" ></span> </span> <span class="longitude"> <span class="value-title" title="-122.419416"></span> </span> </span> </div> Category: <span class="category">Concert</span> </div>

+Quiz


For each RDFa document, draw a knowledge graph.

For each RDFa attribute, trace its meaning with the ontology at http://rdf.data-vocabulary.org/#.

+


• RDFa is RDF in XHTML.

• 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?

RDF On Its Own

+RDF Is All About Making Statements

• An RDF Document contains Statements.

• A statement can be thought of as an ordered triple composed of three items: (resource, property-type, property-value)

• A Resource is anything that can be identified.

• A Predicate is a property name that has a URI. The Predicate may or may not actually be resolvable.

• A Value is another Resource or a literal

• Statements may be represented in RDF XML, abbreviated RDF XML, N-Triples or graphs.


+RDF Triples


(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.

Using RDF Schema we can describe the property names, values and value ranges that are permitted for the property.

+A Simple Description

<RDF>

<Description about = "Some URI">

<creator>property value

</creator>

<title>property value

</title>

</Description>

</RDF>


+Resource Valued Property

<RDF>


<creator rdf:resource =

"www.andrew.cmu.edu/~mm6"/>

</Description>

<Description about = "www.andrew.cmu.edu/~mm6">

<FN>Mike McCarthy</FN>

</Description>

</RDF>


+Making Many Statements<RDF>


<creator>property value</creator>

<title>property value</title>

</Description>


<creator>property value</creator>


</Description>

:

:

</RDF>95-733 Internet Technologies

+Blank Nodes

<RDF>


<creator>

<Description> <!– no about attribute holding a URI

<FN>Joe Smith</FN>

<EMAIL>[email protected]</EMAIL>

</Description>

</creator>

</Description>

</RDF>


+XML Valued Property

<RDF>


<generates rdf:parseType="Literal">

<html><body></body></html>

</generates>

</Description>

</RDF>


+A Type Property

<RDF>

<Description about = ”SomeURL">

<rdf:type rdf:resource=

"http://www.schemas.org/www/WebPage"/>

</Description>

</RDF>


+An Abbreviated Type Property

<RDF>

<TypeName about = "Some URI">

<creator>property value

</creator>


</TypeName>

</RDF>


+RDF has several notations:

• Natural language (English, Spanish,…)

• RDF XML

• Abbreviated RDF XML

• N-Triples

• Graph


+Another RDF Application CC/PP


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.


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

CC/PP

RDF

XML

CC/PP provides a model for formalizing device profiles.


• 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

+Processing RDF in Java

XSLT?

DOM?

SAX?

StAX?

Open source Jena from HP Research provides another approach


+Jena Example 1

// Modified from HP's Jena Tutorial

// ~/mm6/www/95-733/examples/Jena

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.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>

Notes:16fa… is a blanknode with familyand given properties.The main resource hasa blank node as the value of the N property.The main resource alsohas a FN property witha value.

+Reading OWL with Jena


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 Web


The 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 Web


An 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.

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