Department of Computer Science, University of Maryland, College Park

1

Sharath Srinivas- CMSC 818Z, Spring 2007

Semantic Web and Knowledge Representation

Outline

MotivationIntroductionInformation centric perspective of

semantic webArchitecture of the Semantic WebFutureVideo and examples!

Motivation

Is there any such task that a computer can do, which a human cannot do? …

5 possible answers: Yes, of course! Not at all Sort of, but most tasks that humans do cannot be done by

computers. Sort of, but most tasks that humans do can be done by

computers No Comments!

Why is it so?All Computers do is what they are

programmed to do!

This is the state of affairs today

Motivation…

So, are computers dumb?

Yes…sort of!

Then why are we (Computer Scientists) spending our life on something that’s dumb?

To make them less dumb!!!

Introduction

The Web is considered to be the most powerful information tool in history.

One of the most difficult resources to search and evaluate

“The ultimate goal of the  Web will be achieved when search engines can find the answer to the question of Life, the Universe and Everything else - obviously that will occur in Web 42.0” –Prof. Jim Hendler, MIND lab

Introduction

Web 42.0 ???

What is “Web 42.0”?

What is the current version of the web? I decided to search for this on google…

No useful results

So I decided to post this question on a forum where people discuss stuff like this…

Response…

Intelligent Search

So, we need more intelligent search engines, that can understand the users

Google Answers example:

searching for words isn’t really what you want to do. You’d like to search for ideas, for concepts, for solutions, for answers…

Current information representation and retrieval techniques are not capable of achieving this.

Need of the hour?

We need more intelligent Systems that can retrieve quality information.

For this we need better representation techniques of information.

Information is not data, it is knowledge derived from data.

Information Dynamics

Information

Representation

Information

Representation

Loss During transformation

into its Representation

?

Information Dynamics

Ideal Scenario

Information Dynamics…

Information

Representation

Information

Representation

Will this ever be possible?

Semantic

semantic, a. and n.

a. Relating to signification or meaning.

Semantic…

Making web pages machine readable

Combining information from multiple sources

Making inferences to find new knowledge

Semantic Web…

My Web Page

Advisor 1’s web Page

Advisor 2’s web Page

My Web Page (which is a autonomous intelligent agent) should determine whom I should meet and at what time.

Wedding Cake!

Pieces of the cake…

Parts of the Semantic Web:A Global naming schema (URI)A standard syntax for describing data (RDF)A syntax for representing the properties of

the data (RDF Schema)A standard means of describing the

relationships between data (OWL)

XML: User definable and domain specific markup

HTML:<H1>Introduction to AI</H1>

<UL> <LI>Teacher: Frank van Harmelen<LI>Students: 1AI, 1I<LI>Requirements: none

</UL>

<H1>Introduction to AI</H1><UL> <LI>Teacher: Frank van Harmelen

<LI>Students: 1AI, 1I<LI>Requirements: none

</UL>

<course><title>Introduction to AI</title><teacher>Frank van Harmelen</teacher><students>1AI, 1I</students><req>none</req>

</course>

<course><title>Introduction to AI</title><teacher>Frank van Harmelen</teacher><students>1AI, 1I</students><req>none</req>

</course>

XML:

XML document= labelled trees

<course date=“...”><title>...</title><teacher>...</teacher>

<name>...</name><http>...</http>

<students>...</students></course>

Syntax versus Semantics

Syntax: the structure of your data Semantics: the meaning of your data Two conditions necessary for interoperability:

Adopt a common syntax: this enables applications to parse the data.

Adopt a means for understanding the semantics: this enables applications to use the data.

RDF

RDF…

RDF…combining Information

RDF…combining Information

RDF…combining Information

RDF…combining Information

RDF…combining Information

Wedding cake…

RDF SChema

Wedding cake…

Ontology

Ontology“... a specification of a

conceptualisation.”Vocabulary and relationshipsRDFSClasses and subclass relationshipsProperties and subproperty relationshipsRange and domain of properties

Ontology…example

Person

Student Researcher

subClassOfsubClassOf

Jeentype

hasSuperVisordomain range

Frank

type

hasSuperVisor

Ontology

Identity (owl:sameAs)Disjunctionsomething can be in one or other class

but not bothNumber restrictionsat least n of some propertyno more than n of some propertyFlavours: OWLLite, OWLDL,OWLFull

What you can do

Mark up web pagesPresent databases as RDFUse and develop new ontologies

Wedding cake…

Logic, Proof and Reasoning

Wedding cake…Revisited!!

Proof, Logic and reasoning are active areas of research

Trust

Self Intelligent agents: Can we trust them?

Don’t drive! Weather is bad

Should I trust my agent?

Conclusion

Semantic web is no hype

Its already a reality

It is and it will continue to make Computers less dumb!

References and Resources

MindLabs and Mindswap: Google it!

Wikipedia: Google Search: Semantic web Wiki

The talk given by Hugo Mills at the Hampshire Linux Users group: Cannot find using google…

www.hantslug.org.uk/cgi-bin/wiki.pl?TechTalks/3rdJune2006