Creating Linked Data Juan F. Sequeda Semantic Technology Conference June 2011

Linked Data is a set of best practices to publish and interlink data on the web

Linked Data Principles 1.Use URIs as names for things 2.Use HTTP URIs so that people can look up (dereference) those names. 3.When someone looks up a URI, provide useful information. 4.Include links to other URIs so that they can discover more things.

1) Use URIs as names for things

Uniform Resource Identifiers identify real world objects and abstract concepts – Not only web documents and digital content – People, places, locations, my car – Know somebody, from somewhere

1) Use URIs as names for things

1) Use URIs as names for things – Identifies the person – Identifies an RDF document

2) Use HTTP URIs so that people can look up (dereference) those names.

HTTP protocol is the Web’s universal access mechanism Linked Data only uses HTTP URIs – URI: unique name – HTTP URI: universal means of access to the URI HTTP URIs should be dereferencable

Dereference a URI?

What’s with the redirection?

RDFa … The trouble with Bob Alice …. …

Minting HTTP URIs If you own the domain name and run a web server at that location, mint URIs in this namespace I own the domain mycompany.com I run a webserver I now can mint URIs in this namespace: –

Create Cool URIs If you don’t control a namespace, don’t misuse it – Avoid implementation details – 123&format=rdf 123&format=rdf Use Natural Keys within URI – –

Three different URIs URI for the real world object (non-information resource) – – – – URI for the HTML document (information resource) that describes the real world object – – – URI for the RDF document (information resource) that describes the real world object – – – –

3) Provide useful information

How do we provide useful information in document form on the web?  HTML How do we provide useful information in data form on the web  RDF Different ways of serializing RDF – RDF/XML – RDFa – N3 – turtle

RDF subject – predicate – object Coldplay is the artist of Viva la Vida

prefix dbpedia-owl: prefix foaf: prefix dbprop: prefix geo: dbpedia-owl:artistfoaf:name dbprop:origin geo:longgeo:lat “Coldplay”

. <dbpedia-owl:Band xmlns:dbpedia-owl=" rdf:. a ;. ntriples RDF/XML turtle

HTML My name is Bob Smith, but people call me Smithy. Here is my home page: I live in Albuquerque, NM and work as an engineer at ACME Corp. My friends: Darryl, Edna

RDFa (RDF in HTML) My name is Bob Smith, but people call me Smithy. Here is my homepage: I live in Albuquerque, NM and work as an engineer at ACME Corp. My friends: Darryl, Edna

What to publish? Literal Triples “Coldplay” Outgoing Links Incoming Link

What to publish? Description of the data set – Semantic Sitemaps – voiD (Vocabulary of Interlinked Datasets) Provenance Metadata Licenses Information

Vocabularies (or Schemas or Ontologies) Create your own using – Simple Knowledge Organization Systems (SKOS) Taxonomy – RDF Vocabulary Description Language (RDF Schema) Light weight vocabularies – Web Ontological Language (OWL) Highly expressive and capable of inferencing

Vocabularies (or Schemas or Ontologies) Reuse vocabularies – Dublin Core: metadata attributes – Friend of a Friend (FOAF): persons and relationships – Semantically Interlinked Online Communities (SIOC): describing users, posts, blogs, etc – Description of a Project (DOAP) – Music Ontology – Programmes Ontology: TV and radio programs – Good Relations: describing products and services – Review Vocabulary – Basic Geo (WGS84) Vocabulary

4) Include links to other things

Set external RDF links into other data sources on the Web – Subject of the triple is in the namespace of one data set – Object of the triple is a URI in the namespace of another data set Connect siloed data islands Enable discovery

4) Include links to other things Relationship Links Identity Link Vocabulary Links

Which predicate for linking to choose? Depends on your domain Is it widely used? – owl:sameAs – foaf:knows – foaf:based_near – … If you create your own, relate it to a widely used predicate

How to create the links? Manually – Works for small and static data sets – I want to find another URI that identifies the same real object that I have Sindice and Falcons provide index of URIs by keyword (Semi) Automatic – Record Linkage/Identity Resolution/Co-reference – Silk: – LIMES: