RDF For Semantic Web Dhaval Patel 2nd Year Student School of IT IIT Kharagpur 21/09/2018 patelc@sit.iitkgp.ernet.in

Presentation Outline Introduction Syntactic Web Semantic Web Basic RDF Terminology RDFS Reference 21/09/2018 patelc@sit.iitkgp.ernet.in

Introduction TBL’s Original vision of the Web ……a goal of the Web was that, if the interaction between person and hypertext could be so intuitive that the machine-readable information space gave an accurate representation of the state of people's thoughts, interactions, and work patterns, then machine analysis could become a very powerful management tool, seeing patterns in our work and facilitating our working together through the typical problems which beset the management of large organizations….. (from w3c) Realising this vision, which has become known as the “Semantic Web” 21/09/2018 patelc@sit.iitkgp.ernet.in

Syntactic Web Current Web Contents are represented using Natural Language (English…) Graphics, Multimedia Human can Process this information easily Combine information easily from various source (Even information is represented using different Technologies / Format) For Machine Difficult to make a sense from image Drawing Analogy automatically is Difficult and many more… Example: False Hit on Google Search Engine 21/09/2018 patelc@sit.iitkgp.ernet.in

Semantic Web …An article in May 2001 issue of Science and Technology at Scientific American… Article Title The Semantic Web A new form of Web content that is meaningful to computers will unleash a revolution of new possibilities Author Tim Berners-Lee, James Hendler and Ora Lassila 21/09/2018 patelc@sit.iitkgp.ernet.in

Definition Semantic Web is Extension of the current Web Information is given well-defined meaning Enabling computers and people to work in cooperation Aim of Semantic Web Medium of data and information that can be processed automatically Imp. For Semantic Web Knowledge Representation Examples Automatic Assistance, Data Integration, Digital Library, Semantic of Web Services (“find me the most elegant credit card verification service?”) 21/09/2018 patelc@sit.iitkgp.ernet.in

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Giant Working for Semantic Web Tim Berners-Lee Dan Brickley Dan Connolly Sandro Hawke Jose Kahan Marja Koivunen, Eric Miller Eric Prud'hommeaux 21/09/2018 patelc@sit.iitkgp.ernet.in

What is Needed? Each resource describe itself Means Provide information It is also Called as Meta Data Meta Data is in machine process able format Vocabulary about the meta data should be defined Agent is able to reason about the meta data How to make Metadata Machine Process able Format Define Unambiguous Name (URI) Data Model (RDF – To Express Metadata) Common Vocabulary (Ontology) The “Semantic Web” is a metadata based infrastructure for reasoning on the Web 21/09/2018 patelc@sit.iitkgp.ernet.in

Semantic Web is Not AI on Web Use element of Logic SW is mainly about the representing and characterizing metadata AI is using the Metadata of SW SW Principles Any abstract thing can have a URI#xxx Vocabularies can merge and be replaced with time Anyone can say anything about anything No one system knows everything Design must be minimalist 21/09/2018 patelc@sit.iitkgp.ernet.in

RDF – Resource Description Framework RDF is graphical formalism For representing metadata It is the “Official” W3C format For describing the semantics of information in a machine accessible way It represent metadata as a set of statements Statements Statements are <subject, properties, object> triples Subject = Object = Resource (An element, URI, Literal) (a document, a picture, a paragraph on the Web) Statements describe properties of Resource Properties is directed relations between two resources Properties themselves are also resources (URIs) 21/09/2018 patelc@sit.iitkgp.ernet.in

RDF Graph 21/09/2018 patelc@sit.iitkgp.ernet.in

XML Representation of RDF Graph 21/09/2018 patelc@sit.iitkgp.ernet.in

Encoding Style of RDF Graph «Element for #FullSlide» «Element for graphics Type» Chart «/Element for graphics Type» «/Element for #FullSlide» «Element for #FullSlide» «Element for labelledBy» «Element for #BottomLegend» «/Element for labelledBy» «/Element for #FullSlide» 21/09/2018 patelc@sit.iitkgp.ernet.in

Example <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> <rdf:Description rdf:about="#FullSlide"> <axsvg:labelledBy> <rdf:Description rdf:about="#BottomLegend"/> </axsvg:labelledBy> </rdf:Description> <rdf:RDF> 21/09/2018 patelc@sit.iitkgp.ernet.in

Chaining of Resource <rdf:Description rdf:about="#FullSlide"> <axsvg:labelledBy> <rdf:Description rdf:about="#BottomLegend"/> </axsvg:labelledBy> </rdf:Description> <rdf:Description rdf:about="#BottomLegend"> <axsvg:isAnchor>True</axsvg:isAnchor> 21/09/2018 patelc@sit.iitkgp.ernet.in

Simplification <property> <rdf:Description rdf:about="URI"/> </property> Simplified As <property rdf:resource="URI"/> 21/09/2018 patelc@sit.iitkgp.ernet.in

Programming Practice Python + RDFLib PHP Java 21/09/2018 patelc@sit.iitkgp.ernet.in

RDF Schema (RDFS) Also known as RDF Vocabulary Description Language (RDFS) In RDF, Some words may be incorrect or unknown Interpretation is an arbitrary binary relation Not given any special meaning to vocabulary such as sub-Class-Of or type RDF Schema defines “schema vocabulary” that supports definition of ontologies Gives “extra meaning” to particular RDF properties and resources (such as subClassOf) This “extra meaning”, or semantics, specifies how a term should be interpreted 21/09/2018 patelc@sit.iitkgp.ernet.in

RDF Schema Terms (Construct) Class Property type Sub Class Of range domain <Person, type, Class> <hasColleague, type, Property> <Professor, subClassOf, Person> <Carole, type, Professor> <hasColleague, range, Person> <hasColleague, domain, Person> 21/09/2018 patelc@sit.iitkgp.ernet.in

Vocabulary 21/09/2018 patelc@sit.iitkgp.ernet.in

Point to be Taken care <Species, type, Class> No Distinction Between Class and Resource <Species, type, Class> <Lion, type, Species> <Leo, type, Lion> Properties has themselves properties No Difference Between Construct and user defined Construct <Property , type, Class> 21/09/2018 patelc@sit.iitkgp.ernet.in

Continue …… Problem with RDFS No transitive, inverse or symmetrical ( IsPartof, hasPart) Ontology Web Ontology Language 21/09/2018 patelc@sit.iitkgp.ernet.in

Reference [1] http://www.sciam.com/article.cfm [1] http://www.sciam.com/article.cfm [2] http://www.w3.org/RDF [3] http://www.w3.org/Consortium/Offices/Presentations/RDFTutorial [4] http://www.w3.org/2001/sw/EO [5] http://www.w3.org/2002/Talks/04-sweb-sloan/ 21/09/2018 patelc@sit.iitkgp.ernet.in