Semantic Web Example

wrendeceitInternet και Εφαρμογές Web

21 Οκτ 2013 (πριν από 3 χρόνια και 7 μήνες)

78 εμφανίσεις

By

Ahmet Can Babao
ğ
lu

Abdurrahman Be
ş
inci


Suppose you want to buy a Star wars DVD having such
properties;


wide
-
screen ( not full
-
screen )


the extra disc of bonus materials


lowest available price


not paying too much for shipping and handling


not waiting too long for delivery.

What would you do?


The best thing you can do is to search for web pages and
look for a suitable item.


However, using semantic web, agents can return the suitable
results to you…


An agent lists the prices of flat screen HDTVs
with properties;


larger than 40 inches with 1080p resolution


at shops in the nearest town


open until 8pm on Tuesday evenings



Find and buy a airline ticket if there is a route


from Istanbul to London


this evening with price lower than $150

Tim Berners
-
Lee (1998 )



I
nventor of WWW, URIs, HTTP, and HTML


T
he director of the World Wide Web
Consortium

( www.w3.org )


S
enior researcher at the MIT Computer
Science and Artificial Intelligence Laboratory


A

Web

that

includes



documents
,

or

portions

of

documents
,



describing

explicit

relationships

between

things

and


containing

semantic

information

intended

for



automated

processing

by

our

machines
.



TBL’s

words
;

Now

web

is

a

huge

book,

with

semantic

web,

it

will

be

a

huge

database
.


A

technology

helps

machines

`understand`
;


The

Beatles
was

a popular
band

from

Liverpool.


John
Lennon

was

a
member

of
the

Beatles.



Machine process
-
able


Data integration


Meaningful web pages


Making deductions


SW is not AI and AI is not SW


SW should be a great playground for AI




Web of data
-

provides common data
representation framework to facilitate
integrating multiple sources to draw new
conclusions


Increase the utility of information by
connecting it to its definitions and to its
context


More efficient information access and
analysis


Agents searching Web and retrieving valuable
information to the end user.


Web services publishing their information


Programs running to merge data of different
web services and create new results from
them.


User
:
Exciting world
-

semantics of the

resource, understood


from content


Machine:
Very little information available , only links



User:
Even more exciting world, richer user experience


Machine:
More processable information is available (Data Web)



Metadata layer ( Resource and property )



RDF ( Resource Description Framework )


Schema layer



(

H
ierarchical description of concepts
)



RDF
-
S ( RDF Schema )


Logical layer ( class relations, uses logic )



OWL ( Web Ontology Language )




XML:
uses tags to describe data


RDF:

1.
provides a framework to describe
resources
.

2.
uses
triples

written as XML tags to express this information
as a
graph
.


Q:
There is a father relation between Anakin and Luke ok but,
who or what is Anakin and Luke ? What does father mean
anyway?

A:
RDF uses
uniform resource identifiers (URIs)

to direct the
computer to a document or object that represents the
resource.



Computers don't have the kind of vocabulary that
people do. So the computer has to have
documents

that
describe all the words and
logic

to make the necessary
connections.


RDF
-
S:
adds classes, subclasses and properties to
resources, creating a basic language framework


OWL:
formalizes ontology, describes relationships between
classes and uses logic to make deductions. It can also
construct new classes based on existing information.


<http://aaronsw.com/>


<http://love.example.org/terms/reallyLikes> <http://www.w3.org/People/Berners
-
Lee/Weaving/> .


Explanation;

The first URI is the subject. the subject is me.

The second URI is the predicate. It is "reallyLikes."

The third URI is the object. The object is Tim Berners
-
Lee's book "Weaving the Web." So the
RDF statement above says that I really like "Weaving the Web.“


RDF code;

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

<rdf:Description rdf:about="http://aaronsw.com/">

<love:reallyLikes rdf:resource="http://www.w3.org/People/Berners
-
Lee/Weaving/" />
</rdf:Description>

</rdf:RDF>



To declare a vocabulary or properties


specify the (multiple)
-
inheritance links between the types of
classes (subClassOf or subProperty);


machines determine

the meanings of resources

based on properties and

classes.



<rdf:RDF xml:base="http://www.inria.fr/2007/04/17/humans.rdfs" xmlns:rdf
="http://www.w3.org/1999/02/22
-
rdf
-
syntax
-
ns#"
xmlns:rdfs="http://www.w3.org/2000/01/rdf
-
schema#"
xmlns="http://www.w3.org/2000/01/rdf
-
schema#">



<Class rdf:ID="Man">


<subClassOf rdf:resource="#Person"/>



<subClassOf rdf:resource="#Male"/>


<label xml:lang="en">man</label>



<comment xml:lang="en">an adult male person</comment> </Class>


<rdf:Property rdf:ID="hasMother">


<subPropertyOf rdf:resource="#hasParent"/>


<range rdf:resource="#Female"/> <domain rdf:resource="#Human"/>


<label xml:lang="en">has for mother</label>


<comment xml:lang="en">to have for parent a female.</comment>


</rdf:Property> </rdf:RDF>


We declare a class #Man, sub class of #Person and #Male, and a property #hasMother
having sub property of #hasParent, and that is used between instances of the class
#Human and instances of the class #Female.



making logical deductions. For instance, given the ontology above, a
Semantic Web agent could infer that since "Goose" is a type of
"DarkMeatFowl," and "DarkMeatFowl" is a subset of the class "Fowl,"
which is a subset of the class "EdibleThing," then "Goose" is an
"EdibleThing."


<owl:SymmetricProperty rdf:ID="sibling">


<rdfs:domain rdf:resource="#Animal" />


<rdfs:range rdf:resource="#Animal" />
</owl:SymmetricProperty>


A property is symmetric.




Precise search results


Time efficient for human


Easy to publish information


More human like thinking ( one step closer )


Data integration


Machine process
-
able


The learning curve. RDF was developed by people with
academic background in logic and artificial intelligence. For
traditional developers it is not very easy to understand.


All the web pages’ content must be changed which is a long
process.


Unrealized idea; "This simple idea, however, remains largely
unrealized."


Two formats for one piece of data: one for human viewing
and one for machines


concerns regarding censorship and privacy (for governments
to control the viewing and creation of online information )


Semantic Web infrastructure
-

stimulate the
network effect of data


Data Access


Best Practices for vocabulary / ontology
development


Development of ontology registries for
Open
vocabularies