Web == One huge DB

A seminar on Linked Data and Semantic Web

The Web of Linked Documents

Issues of Linked Documents

Loosely structured Data

Unstructured hyperlinks

Disconnected Data

What is Semantic Web?

The first step is putting data on the Web in a form that machines can naturally understand, or converting it to that form. This creates what I call a Semantic Web a web of data that can be processed directly or indirectly by machines. ~ Tom Heath

The Web of Linked Data

The Semantic Web

This converts the whole web into a single database.

Designed for machines and humans.

Links between things-things and things-and its description.

Encourages reuse, reduces redundancy

Enables to add more value to data over the network.

Linked Data Technology Stack

URIs

HTTP

RDF (Resource Description Framework)

RDFS/OWL

URIs Not Just for Web Pages

A Uniform Resource Identifier (URI) provides a simple and extensible means for identifying a resource. -- RFC 3986

Exampleshttp://dbpedia.org/resource/Tim_Berners-Lee

http://dbpedia.org/resource/Model_Engieering_College

http://sws.geonames.org/4671654/

HTTP

Data access mechanism

Using http:// URIs to identify things allows people to look these things up

RDF: Resource Description Framework

Data format for describing things and their interrelations.

Descibes relations based on triples; subject-predicate-object

The RDF Data Model

subject predicate objectTom worksFor TalisTalis basedIn Birmingham eg:

Data Merging with RDF

Consider a profile of Richard

Data Merging with RDF

This can be naturally merged

Data Merging with RDF

This is linked Data

Data discovery in RDF

Advantages of RDF

Information in different sources merge naturally

Clients can look up every URI in and RDF graph over the Web to get addictional info.

Easy description of relations with the help of RDFS

Linked Data principles

Use HTTP URIs

Provide useful information in RDF

Include RDF links to other URIs

Why publish Linked Data?

Ease of discovery

Ease of consumptionstandards-based data sharing

Reduced redundancy

Added valuebuild ecosystems around your data/content

The Linking Open Data Project

The Linking Open Data Project

Community project with W3C support

Take existing open data sets

Make them available on the Web in RDF

Interlink them with other data sets

Began early 2007

LOD Cloud as on November 2007

LOD Cloud as on March 2008

LOD Cloud as on March 2009

The latest LOD cloud as on July 2009

Setting RDF links

RDF links enable LD browsers and crawlers to discover additional data

The application domain determine the RDF properties used in predicate section.eg: for describing people : foaf:knows, foaf:based_near

for showing another same data source: owl:sameAs

We can set the RDF links manually and generate links automatically using algorithms.

Generating RDF links manually

Identify the datasets you want to link to.

Search for the right URIs to link to using search interfaces if provided. Or using LD browsers

Use services like Uriqr to search for existing URIs and choose the most popular one suiting your need.

Auto generating RDF links

Used on Large datasets

Two major methodsPattern Based algorithmSearches the URIs on various data sets for similar patterns and link generate the RDF links

Property based algorithmsSearches additional informations of the resource at the resource end points rather than the URIs alone.Eg: interlinking Dbpedia and Geonames.

Now how to put it on Linked Data

Serve as static filesSimplest way is to produce static RDF files and upload them to your webserver.When creating FOAF profiles, and RDF vocabularies

RDF is generated by some other software.

Serving RDB onThe conventional DB is untouched

A mapping is done to produce the RDF files.

Tools like D2R server and OpenLink Virtuoso is used.

RDB to Linked Data

SPARQL

SPARQL Protocol and RDF Query Language

Retrieves data from RDF

Similar to SQL syntaxEg:

PREFIX foaf:

SELECT ?acquaintanceFROM WHERE {< http://w3.org/People/Berners-Lee/card#i> foaf:knows ?acquaintance .FILTER isURI(?acquaintance)}

Linked Data Applications

Linked Data Applications

Browsers Marbles

Search enginesFalcons

MashupsDbpedia Mobile

Talis Aspire

DERI pipes

Challanges

User Interface

Link Maintenance

Licensing

Trust, Quality, Relevance

Conclusions

Linked Data will enable revolution on how data will be used

Machines will finally be able to search!!

Researchers can have a wide range of related data to dig into.

RAW DATA
NOW!

~Tim Berners