The Semantic Web. Mansooreh Jalalyazdi

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1 1 هو العليم

2 2 The Semantic Web Mansooreh Jalalyazdi

3 3 Content Syntactic web XML Add semantics Representation Language RDF, RDFS OWL Query languages

4 4 History of the Semantic Web Tim Berners-Lee vision for the future of the web: To make the Web a more collaborative medium To make the Web understandable, and thus processable, by machines.

5 5 Where we are Today: the Syntactic Web

6 6 The Syntactic Web is A hypermedia, a digital library A library of documents called (web pages) interconnected by a hypermedia of links A database, an application platform A common portal to applications accessible through web pages, and presenting their results as web pages A platform for multimedia BBC Radio 4 anywhere in the world! Terminator 3 trailers! A naming scheme Unique identity for those documents A place where computers do the presentation (easy) and people do the linking and interpreting (hard). Why not get computers to do more of the hard work?

7 7 What is the Problem? Markup consists of: rendering information (e.g., font size and colour) Hyper-links to related content Semantic content is accessible to humans but not (easily) to computers

8 8 What information can we see WWW2002 The eleventh international world wide web conference Sheraton waikiki hotel Honolulu, hawaii, USA 7-11 may location 5 days learn interact Registered participants coming from australia, canada, chile denmark, france, germany, ghana, hong kong, india, ireland, italy, japan, malta, new zealand, the netherlands, norway, singapore, switzerland, the united kingdom, the united states, vietnam, zaire Register now On the 7 th May Honolulu will provide the backdrop of the eleventh international world wide web conference. This prestigious event Speakers confirmed Tim berners-lee Tim is the well known inventor of the Web, Ian Foster Ian is the pioneer of the Grid, the next generation internet

9 9 What information can a machine see

10 Solution: XML markup with meaningful tags? <name> </name> <location> </location> <date> </date> <slogan> </slogan> <participants> </participants> <introduction> </introduction> <speaker> </speaker> <bio> </bio> That is, structure and semantics of documents are interwoven Agree upon the meaning of tags through the use of namespaces 10

11 11 Need to Add Semantics External agreement on meaning of annotations E.g., Dublin Core Agree on the meaning of a set of annotation tags Title: A name given to the resource. Creator: An entity primarily responsible for making the Subject: The topic of the content of the resource. Description: An account of the content of the resource.. Problems with this approach Inflexible Limited number of things can be expressed

12 12 Need to Add Semantics (Cont.) Motivation toward RDF(S), DAML+OIL, OWL, - Establish a widely accepted standard for representing expressive declarative knowledge on the Web. Knowledge Representation Knowledge sharing Communication Language for query

13 RDF RDF stands for Resource Description Framework Allows us to create very rich, deeply nested information structures that describe web resources

13 13 RDF RDF stands for Resource Description Framework Allows us to create very rich, deeply nested information structures that describe web resources RDF is graphical formalism ( + XML syntax + semantics) for representing metadata for describing the semantics of information in a machine- accessible way

14 The RDF Data Model Statements are <subject, predicate, object> triples: <http://www.example.org/index.html> <http://purl.

14 14 The RDF Data Model Statements are <subject, predicate, object> triples: < < John Smith Can be represented as a graph: has a creator whose value is John Smith

15 15 RDF Example: More Information About John Smith

16 16 RDF Example (Cont.) <?xml version="1.0"?> <rdf:rdf xmlns:rdf=" xmlns:dc= xmlns:exterms=" <rdf:description rdf:about=" <dc:creator rdf:resource=" </rdf:description> <rdf:description rdf:about=" "> <exterms:name>john Smith</exterms:name> <exterms:age rdf:datatype="&xsd;integer"> 27</exterms:age> </rdf:description> </rdf:rdf>

17 17 RDFS RDFS extends RDF with schema vocabulary, e.g.: Class Property Type SubClassOf SubPropertyOf Range Domain RDFs provides a simple and basic modeling language for ontologies

18 18 RDFS Example A Vehicle Class Hierarchy

19 19 RDFS Example (Cont.).. <rdfs:class rdf:id="motorvehicle"/> <rdfs:class rdf:id="passengervehicle"> <rdfs:subclassof rdf:resource="#motorvehicle"/> </rdfs:class>.. <rdfs:class rdf:id="minivan"> <rdfs:subclassof rdf:resource="#van"/> <rdfs:subclassof rdf:resource="#passengervehicle"/> </rdfs:class>.. <rdf:property rdf:id="registeredto"> <rdfs:domain rdf:resource="#motorvehicle"/> <rdfs:range rdf:resource="#person"/> </rdf:property> <rdf:property rdf:id="driver"> <rdfs:domain rdf:resource="#motorvehicle"/> </rdf:property> <rdf:property rdf:id="primarydriver"> <rdfs:subpropertyof rdf:resource="#driver"/> </rdf:property>

20 20 Problems with RDFS RDFS too weak to describe resources in sufficient detail No localised range and domain constraints Can t say that the range of haschild is person when applied to persons and elephant No existence/cardinality constraints Can t say that all instances of person have a mother that is also a person, or that persons have exactly 2 parents No transitive, inverse or symmetrical properties Can t say that ispartof is a transitive property, that haspart is the inverse of ispartof or that touches is symmetrical

21 21 Ontology Ontology is a term borrowed from philosophy that refers to the science of describing the kinds of entities in the world and how they are related An OWL ontology may include descriptions of classes, properties and their instances.

22 22 What is Ontology... an ontology is a formal, explicit specification of a shared conceptualization Gruber Conceptualization refers to an abstract model of phenomena in the world by having identified the relevant concepts of those phenomena. Explicit means that the type of concepts used, and the constraints on their use are explicitly defined. Formal refers to the fact that the ontology should be machine readable. Shared reflects that ontology should capture consensual knowledge accepted by the communities

23 OWL Example <owl:class rdf:id="fruit"> <owl:unionof rdf:parsetype="collection"> <owl:class rdf:about="#sweetfruit" /> <owl:class rdf:about="#nonsweetfruit" /> </owl:unionof> </owl:class>

23 23 OWL Example <owl:class rdf:id="fruit"> <owl:unionof rdf:parsetype="collection"> <owl:class rdf:about="#sweetfruit" /> <owl:class rdf:about="#nonsweetfruit" /> </owl:unionof> </owl:class> <owl:objectproperty rdf:id="adjacentregion"> <rdf:type rdf:resource="&owl;symmetricproperty" /> <rdfs:domain rdf:resource="#region" /> <rdfs:range rdf:resource="#region" /> </owl:objectproperty> <Region rdf:id="mendocinoregion"> <locatedin rdf:resource="#californiaregion" /> <adjacentregion rdf:resource="#sonomaregion" /> </Region>

24 Thank You! 24

LECTURE 03 XML: FIRST LAYER OF SEMANTIC WEB

SEMANTIC WEB LECTURE 03 XML: FIRST LAYER OF SEMANTIC WEB IMRAN IHSAN ASSISTANT PROFESSOR AIR UNIVERSITY, ISLAMABAD WHERE ARE WE TODAY? THE SYNTACTIC WEB 2 SW S16 03 - XML 1 WHAT IS THE PROBLEM? CONSIDER