Semantic Web and Ontology:What, Why and How
Manu Madhavan
Asst.Professor,Dept. of Computer Science and Engg.
Sreepathy Institute of Management And [email protected]
7 Oct, 2013.
Manu Madhavan Semantic Web and Ontologly
Are you satisfied with current search ?
Does Googling always give you required results?
Do you thing current web services are enough for your works?
what you require otherwise ?
Manu Madhavan Semantic Web and Ontologly
What Stops Us From Doing More?
Traditional Web is entirely aimed for reading and is purelydisplay oriented.
HTML Tags doesn’t carry any information about the content
Search is merely keyword matching. Page ranking does notconsider the context.
Computers can only present users with information, but theycannot “understand” the information well enough to displaythe data that is most relevant in a given circumstance.
Manu Madhavan Semantic Web and Ontologly
Think a minute....
Whether it is possible to reconstruct the Web by adding someinformation into the documents stored on the Internet so that thecomputers can use this extra information to understand what agiven document is really about? YES !!! Solution is Semantic
Web
Manu Madhavan Semantic Web and Ontologly
Think a minute....
Whether it is possible to reconstruct the Web by adding someinformation into the documents stored on the Internet so that thecomputers can use this extra information to understand what agiven document is really about?
YES !!! Solution is Semantic Web
Manu Madhavan Semantic Web and Ontologly
Semantic Web
The Semantic Web is an extension of the current Web inwhich information is given well-defined meaning, betterenabling computers and people to work in cooperation.
Tim Berners–Lee
The Semantic Web is not about links between web pages. Itdescribes the relationships between things (like A is a part ofB and Y is a member of Z) and the properties of things (likesize, weight, age, and price)
W3School
Manu Madhavan Semantic Web and Ontologly
Semantic Web
The Semantic Web is an extension of the current Web inwhich information is given well-defined meaning, betterenabling computers and people to work in cooperation.
Tim Berners–Lee
The Semantic Web is not about links between web pages. Itdescribes the relationships between things (like A is a part ofB and Y is a member of Z) and the properties of things (likesize, weight, age, and price)
W3School
Manu Madhavan Semantic Web and Ontologly
How to add semantics to the web ?
The simplest way is provide more information: as Metadata:Data About Data
Then use a special Crawler (search agent) to look themetadata for more information.
Manu Madhavan Semantic Web and Ontologly
Semantic Search ?
Build a common vocabulary:a commonly accepted name for this common vocabulary file isontology
Mark up the web pages with semantics ( use XML and highermarkups)
Build an intelligent crawler ( use NLP techniques)
Manu Madhavan Semantic Web and Ontologly
Building Blocks
Ontology
Resource Description Frame Work (RDF)
Web Ontology Language (OWL)
Reasoners
Manu Madhavan Semantic Web and Ontologly
Ontology
Common vocabulary is represented as Ontology
Representation of Shared conceptualization
Represent relations between entities/ resources
Domain Specific
Manu Madhavan Semantic Web and Ontologly
Resource Description Frame Work
RDF is a language for describing information and resources onthe web.
RDF is structured; i.e., it is machine-understandable.
RDF is an XML-based language for describing informationcontained in a Web resource.
The three main components are: RESOURCE, PROPERTY,and STATEMENT
Manu Madhavan Semantic Web and Ontologly
RDF: Resource
Resource is anything that is being described by RDFexpressions
The name of a resource must be global.
Resource is located by a URI
URI have namespace + “#′′ + localResourceName
eg: www .simplegroups.in/ontoClass#Book .
Manu Madhavan Semantic Web and Ontologly
RDF: Property
Property is a resource that has a name and can be used as aproperty
It can be used to describe some specific aspect, characteristic,attribute, or relation of the given resource.
URI have namespace + “#′′ + PropertyName
eg: www .simplegroups.in/ontoClass#hasAuthor .
Manu Madhavan Semantic Web and Ontologly
RDF: Statement
An RDF statement is used to describe properties of resources.
resource (subject) + property (predicate) + property value(object)
〈subject〉 has a property 〈predicate〉, whose value is 〈object〉eg: 〈www .simplegroups.in/ontoClass/Book#ANSI C 〉〈www .simplegroups.in/ontoClass#hasAuthor〉〈www .simplegroups.in/ontoClass/person#Balagurswami〉 .
Manu Madhavan Semantic Web and Ontologly
Web Ontology Language
OWL = RDF schema + new constructs for expressiveness
OWL build on RDF, with more features to express thesemantics
Semantics is expressed by adding restrictions, class- sub classrelations, cardinality constrains, etc.
The properties can be further expressed as symmetric,transitive, equivalent, inverse etc of other properties.
OWL available in 3 forms: OWL -Lite, OWL - DL and OWL-Full
Manu Madhavan Semantic Web and Ontologly
Reasoners
infer logical consequences from a set of asserted facts oraxioms.
Add OWL property features: inverseOf, sameAs,
subpropertyOf, etc.
e.g.
Event hasBirthDate Dateand hasEvent inversOf hasBirhtDate
Then a reasoner will add:
Date hasEvent Event
Pellet Reasoner is used.
Manu Madhavan Semantic Web and Ontologly
Example: Building an Ontology
Consider the example: [an extract from Wikipedia article aboutSachin Tendulkar, 06-Oct-2013.] .
Tendulkar was born at Nirmal Nursing Home on 24 April
1973. His father Ramesh Tendulkar was a reputed
Marathi novelist and his mother Rajni worked in the
insurance industry. Ramesh named Tendulkar after his
favorite music director, Sachin Dev Burman.
Manu Madhavan Semantic Web and Ontologly
Creating Base Ontology
Identify domain entities
In the example document, Birth, Play, Person, Date,Location
Identify events and relations between events and entities
Person hasEvent Birth
Birth hasBirthDate Date
Birth hasBirthLocation Location
Manu Madhavan Semantic Web and Ontologly
Implementing Base Ontology: Classes
Figure: OWL Representation
Manu Madhavan Semantic Web and Ontologly
Implementing Base Ontology: Adding instances
Figure: Populating Ontology
Manu Madhavan Semantic Web and Ontologly
Open source Tools for Ontology
SWOOP :Ontology Editor, Viewer and Reasoner (Demo)
Protege : Ontology Editor, Viewer and Reasoner
Jena- API: To Create ontology programmatically
Python-RDFLib package can be used for Ontologyapplications (with python)
Manu Madhavan Semantic Web and Ontologly
Jena API
Java API for ontology applications.
It will first create a OWL base ontology model and then addfeatures to this model object.
Model model=ModelFactory.createDefaultModel();OntClass Person=model.addClass(“PERSON”);OntClass Event=model.addClass(“EVENT”);OntClass Birth=model.addClass(“BIRTH”);Event.addSubClass(Birth);ObjectProperty hasBirthDate =
model.addObjectTypeProperty(“hasBirthDate”);hasBirthDate.addDomain(Event);hasBirthDate.addRange(Date);
Manu Madhavan Semantic Web and Ontologly
Conclusion
Semantic Web is an extension to traditional web with moreinformation to machine understandability.
Ontology, RDF and OWL are the three main components ofSemantic Web
Tools like SWOOP, Protege, Jena etc can be used forontology development.
Reasoners are used to infer implicit knowledge from theOntologly.
Manu Madhavan Semantic Web and Ontologly
Top Related