Semantic WebBy

Ahmet Can BabaoğluAbdurrahman Beşinci

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…

Semantic Web Example

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

Other Examples

Tim Berners-Lee (1998 )

Inventor of WWW, URIs, HTTP, and HTML The director of the World Wide Web

Consortium ( www.w3.org ) Senior researcher at the MIT Computer

Science and Artificial Intelligence Laboratory

Invented by

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.

What is semantic web?

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

New Features

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

Goals

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.

Applications

User: Exciting world - semantics of the resource, understood from content

Machine: Very little information available , only links

Current Web

User: Even more exciting world, richer user experience

Machine: More processable information is available (Data Web)

Semantic Web

Metadata layer ( Resource and property )RDF ( Resource Description Framework

) Schema layer

( Hierarchical description of concepts )RDF-S ( RDF Schema )

Logical layer ( class relations, uses logic ) OWL ( Web Ontology Language )

SW Architecture

SW Architecture ( contd. )

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.

XML & RDF

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.

XML & RDF (contd. )

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.

RDF-S & OWL

<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>

RDF Example

To declare a vocabulary or properties specify the (multiple)-inheritance links between the types

of classes (subClassOf or subProperty); machines determine the meanings of resourcesbased on properties and classes.

RDF-S Example

<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.

RDF-S Example ( contd. )

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 Example

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

</owl:SymmetricProperty>

A property is symmetric.

OWL Example

Data merging

Precise search results Time efficient for human Easy to publish information More human like thinking ( one step closer ) Data integration Machine process-able

Advantages

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 )

Problems of SW

Semantic Web infrastructure - stimulate the network effect of data

Data Access Best Practices for vocabulary / ontology

development Development of ontology registries for Open

vocabularies

Future Directions