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Internet Technologies
The Semantic Web and The
Resource Description Framework
(RDF and RDFa)
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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.
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Quick Review

Project 1 made asynchronous requests for shopping cart data –
marked up with XML or JSON

Project 2 made requests for data marked up in XML (RSS).

Project 3 made request on an RESTful data model described with
XML or JSON (Odata)
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Check out: https://www.youtube.com/watch?v=mmQl6VGvX-c

Next, let’s look at RDF.
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First: Let’s get some RDF

curl --include --location --header "Accept:application/rdf+xml"
http://dbpedia.org/resource/Yukihiro_Matsumoto

curl --include --location --header "Accept: application/rdf+xml"
http://dbpedia.org/resource/Hydrogen

curl --include --location --header "Accept: applf+xml"
http://dbpedia.org/resource/Roger_Federer
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For human readable information, see the corresponding

http://en.wikipedia.org/wiki/Roger_Federer
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Each of these stores many many RDF triples.
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S
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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.
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A Knowledge Graph
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Triples
Start Node
Edge Label
End Node
vincent_donofrio
starred_in
law_&_order_ci
law_&_order_ci
is_a
tv_show
the_thirteenth_floor similar_plot_as the_matrix
In Dbpedia, most widely used linking predicates are
owl:sameAs, rdfs:seeAlso, foaf:knows
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Notation 3 (N3) or Turtle Format
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntaxns#> .
@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 .
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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>
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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>
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As A Table
Subject
Predicate Object
----------------------------- -----------
--------
<http://www.princeton.edu> edu:hasDept
<http://www.cs.princeton.edu>
<http://www.princeton.edu>
geo:lat
<http://www.princeton.edu>
geo:long
<http://www.cs.princeton.edu> dc:title
Science"
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"40.35"
"-74.66"
"Department of Computer
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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> .
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A triple may be 3 URI’s

http://dbpedia.org/resource/Billie_Holiday
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http://dbpedia-owl:occupation
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http://dbpedia.org/page/Songwriter
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“Billie Holiday was a song writer.”
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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.
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RDFa is being used today by search engines like Google and
sites like Best Buy.
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From the RDFa W3C Primer
“When web data meant for humans is augmented with hints
meant for computer programs, these programs become
significantly more helpful.”
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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
The rel, in a
link, describes
the relationship
between the
current page
and the linked
page.
<a rel="license" href="http://creativecommons.org/licenses/by/3.0/">
a Creative Commons License
</a>.
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A Link with a Flavor
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Labeling Title and Author
<div>
<h2>The trouble with Bob</h2>
<h3>Alice</h3>
...
</div>
RDFa introduces the
property attribute.
What kind of title? A
title of a person or a
title to land or a title of
a work?
<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>
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+ In RDFa, all property names are, in
fact, URLs.
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Multiple Items Per Page
RDFa provides
@about, an
attribute for
<div about="/alice/posts/trouble_with_bob">
<h2 property="dc:title">The trouble with Bob</h2> specifying the
<h3 property="dc:creator">Alice</h3>
exact URL to
...
which the
</div>
contained
RDFa markup
<div about="/alice/posts/jos_barbecue">
<h2 property="dc:title">Jo's Barbecue</h2>
applies
<div xmlns:dc="http://purl.org/dc/elements/1.1/">
<h3 property="dc:creator">Eve</h3>
...
</div>
</div>
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As a Diagram
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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>
The
</div>
inner about
overrides the
outer about.
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As A Graph
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Blog Contact Info
<div>
<p>
Alice Birpemswick
</p>
<p>
Email: <a href="mailto:alice@example.com">alice@example.com</a>
</p>
<p>
Phone: <a href="tel:+1-617-555-7332">+1 617.555.7332</a>
</p>
</div>
This is mainly useful
for viewing.
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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:alice@example.com">
The Dublin core
has no vocabulary for
describing friendships.
But foaf does.
The typeof is an
alice@example.com</a>
RDFa attribute that is
</p>
specifically meant to
<p>
declare a new data
Phone: <a rel="foaf:phone"
item with a certain
href="tel:+1-617-555-7332">+1 617.555.7332</a>
</p>
type.
</div>
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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
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node has no URL to identify it, so it is called a blank node.
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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>
These people are all
</ul>
</div>
friends of Alice and she
Includes them in her
normal HTML blog.
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Adding RDFa
First,describe
these as
Persons.
<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>
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Add Homepages
Use rel for the link
relationships.
<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>
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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>
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</div>
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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.”
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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.
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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".
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Microformats Compete with RDFa
Not from a standards body. A grassroots effort since
2004.
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.”
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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?
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Google adopted Microformats and
RDFa in 2009
Why? In support of “Rich Snippits”.
“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. “
See the Rich Snippit Testing Tool at :
http://www.google.com/webmasters/tools/richsnippets
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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
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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>
:
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Examples from Google – A Review
of a Pizza Joint
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>
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Be sure to visit:
http://rdf.data-vocabulary.org/rdf.xml
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Examples from Google – A Review
of a Pizza Joint
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>
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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>
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Examples from Google – People
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>
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Examples from Google – People
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>
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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>
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Examples from Google – Events
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>,
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Examples from Google – Events
<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>
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Examples from Google – Events
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
</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>
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Examples from Google – Events
<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>
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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/#.
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RDF On Its Own
• 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?
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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, NTriples or graphs.
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RDF Triples
It is required that each resource have a URI.
http://www.andrew.cmu.edu
http://www.andrew.cmu.edu/~mm6/my.xml#root().child(1)
mailto:mm6@andrew.cmu.edu
urn:isbn:0764532367
(resource, property-type, property-value)
A property is a specific characteristic, attribute
or relationship of a resource. Each property has a specific meaning
that 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.
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A Simple Description
<RDF>
<Description about = "Some URI">
<creator>property value
</creator>
<title>property value
</title>
</Description>
</RDF>
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Resource Valued Property
<RDF>
<Description about = "Some URI">
<creator rdf:resource =
"www.andrew.cmu.edu/~mm6"/>
</Description>
<Description about = "www.andrew.cmu.edu/~mm6">
<FN>Mike McCarthy</FN>
</Description>
</RDF>
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Making Many Statements
<RDF>
<Description about = "Some URI">
<creator>property value</creator>
<title>property value</title>
</Description>
<Description about = "Some URI">
<creator>property value</creator>
<title>property value</title>
</Description>
:
:
</RDF>
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Blank Nodes
<RDF>
<Description about = "Some URI">
<creator>
<Description>
<!– no about attribute holding a URI 
<FN>Joe Smith</FN>
<EMAIL>joes@mycom.com</EMAIL>
</Description>
</creator>
</Description>
</RDF>
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Blank Node example from
Microsoft

The following RDF document creates a blank node to contain multiple types of phone
numbers beneath a parent Phone predicate. The blank node is defined by the empty
rdf:Description element just below the CSF:Phone element:

<?xml version="1.0"?> <rdf:RDF
xmlns:csf="http://schemas.microsoft.com/connectedservices/pm#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"> <rdf:Description
rdf:about="urn:upn_abc">
<csf:Phone>
<rdf:Description>
<csf:Ph
one-Home-Primary>425-555-0111</csf:Phone-Home-Primary>
<csf:PhoneMobile-Other>425-555-0114</csf:Phone-Mobile-Other>
<csf:Phone-OfficeOther>425-555-0115</csf:Phone-OfficeOther>
</rdf:Description>
</csf:Phone>
</rdf:Description> </rdf:RD
F>
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XML Valued Property
<RDF>
<Description about = "Some URI">
<generates rdf:parseType="Literal">
<html><body></body></html>
</generates>
</Description>
</RDF>
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A Type Property
<RDF>
<Description about = ”SomeURL">
<rdf:type rdf:resource=
"http://www.schemas.org/www/WebPage"/>
</Description>
</RDF>
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An Abbreviated Type Property
<RDF>
<TypeName about = "Some URI">
<creator>property value
</creator>
<title>property value</title>
</TypeName>
</RDF>
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RDF has several notations:
•
Natural language (English, Spanish,…)
•
RDF XML
•
Abbreviated RDF XML
•
N-Triples
•
Graph
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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 might
include:
• 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.
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Composite Capability/Preference Profiles (CC/PP)
DEVICE PROFILE
CC/PP provides a model for formalizing device profiles.
CC/PP
RDF
XML
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Composite Capability/Preference Profiles
(CC/PP)
• 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.
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Each variant of the document has a
document profile describing the browser
support it needs to display it
DEVICE PROFILES
DOCUMENT PROFILES
NEGOTIATE CORRECT
CONTENT FOR DEVICES
If none of the document variants are suitable,
existing document may be transformed by style
sheet or tool for the purpose, or new document
generated
DEVICES RECEIVE RIGHT MARK-UP
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Processing RDF in Java

XSLT?

DOM?

SAX?

StAX?

Open source Jena from HP Research provides another
approach
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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
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= "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);
}
}
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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>
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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
String givenName
= "http://somewhere/JohnSmith";
= "John";
String familyName = "Smith";
String fullName
= givenName + " " + familyName;
// create an empty model
Model model = ModelFactory.createDefaultModel();
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// 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))
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// 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() + " ");
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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);
}
}
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D:\McCarthy\www\95-733\examples\Jena>java Tutorial03
16fa474: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
Notes:
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:vcard="http://www.w3.org/2001/vcard-rdf/3.0#" >
16fa… is a blank
<rdf:Description rdf:nodeID="A0">
node with family
<vcard:Given>John</vcard:Given>
and given
<vcard:Family>Smith</vcard:Family>
properties.
</rdf:Description>
<rdf:Description rdf:about="http://somewhere/JohnSmith"> The main resource has
a blank node as the value
<vcard:FN>John Smith</vcard:FN>
of the N property.
<vcard:N rdf:nodeID="A0"/>
The main resource also
</rdf:Description>
</rdf:RDF>
has a FN property with
a value.
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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();
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// 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.
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The Semantic Web
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
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 collections
of 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 other
users.
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The Semantic Web
The challenge of the Semantic Web is to provide a language that expresses both
data 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 define
the relations between concepts and specify logical rules for reasoning about them.
Computers will “understand” the meaning of semantic data on a web page by
following links to specified ontologies.
Consider the statement “a hex-head bolt is a type of machine bolt”. We could encode this
in RDF.
When writing code against traditional XML data, the programmer must know what the
the document author uses each tag for.
Meaning is expressed by RDF, which encodes it in a set of triples.
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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. For
example:
“(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, and
an 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 to
an ontology.
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The Semantic Web
Many automated web based services already exist without semantics, but other programs
such 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 a
service 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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