Linked Data: A short(-ish) introduction

Linked DataA short(-ish) introductionBricolage Project meeting, Bristol, 26 Jan 2012

Pete Johnston Technical Researcher, [email protected]

Document Web Principles

• Use URIs as names of documents• Use http URIs, so that people can use HTTP protocol to

look up those names• When someone looks up a URI, provide the document

(*)• Use document standards, e.g. HTML• Include links to other documents, so that people can

discover more documents

Use URIs as names of documents

http://en.wikipedia.org/wiki/D.H._Lawrence

Use http URIs…

http://en.wikipedia.org/wiki/D.H._Lawrence

Provide the documents

Use document standards

Include links to other docs

• Links typically “untyped”<a href="/wiki/Eastwood,_Nottinghamshire" title="Eastwood,

Nottinghamshire">Eastwood</a>

<a href="/wiki/Lady_Chatterley%27s_Lover" title="Lady Chatterley's Lover">Lady Chatterley's Lover</a>

<a href="/wiki/Joseph_Conrad" title="Joseph Conrad">Joseph Conrad</a>

Occasionally “typed”<link rel="copyright“ href=“http://creativecommons.org/licenses/by-sa/3.0/" />

(*) On “providing the document”: content negotiation

• Client HTTP request for doc includes info about preferences, e.g.• Language (Prefer English, but will accept Spanish)• Media-type (Prefer XHTML, but will accept HTML,

plain text)• Server responds with representation of doc which best

matches preferences

Linked Data Principles (a version!)

• Use URIs as names of things• people, places, concepts, documents… anything!• (avoid URI ambiguity)

• Use http URIs so that people and programs can look up those names

• When a person or program looks up a name, provide (representations of) documents about the things

Linked Data Principles (a version!)

Use data standards: RDF Include typed links to other things

so that people and programs can discover other things

Use URIs as names of things

http://dbpedia.org/resource/D.H._Lawrence

Use http URIs…

http://dbpedia.org/resource/D.H._Lawrence

Provide documents about those things…

Thing:http://dbpedia.org/resource/D.H._Lawrence

Document:http://dbpedia.org/page/D.H._Lawrence

…with representations suitable for people…

…and representations suitable for programs

Use data standards: RDF

• A way to model data• Assertions of relationships between two things• Triples: subject, predicate, object

DH Lawrence has-notable-work Lady Chatterley's Lover

Use data standards: RDF

• Triples: use URIs as “words”/names <http://dbpedia.org/resource/D._H._Lawrence> <http://dbpedia.org/ontology/notableWork> <http://dbpedia.org/resource/Lady_Chatterley

%27s_Lover>• In RDF syntaxes, URIs often abbreviated

• dbpedia:D._H._Lawrence

Use data standards: RDF

• Extensibility of vocabulary• Reuse of vocabulary• “Self-description”

• vocabulary terms described using RDF• Rules for data merging/integration• “Formal semantics”, basis for inferencing

Include typed links to other things

dbpedia:D._H._Lawrence dbp-owl:birthPlace dbpedia:Eastwood,_Nottinghamshire ; dbp-owl:notableWork dbpedia:Lady_Chatterley%27s_Lover ; dbp-owl:influencedBy dbpedia:Joseph_Conrad .

“Linked data is data you can click on”(?John Sheridan, National Archives)

Linked Data from British Library: D. H. Lawrence

Linked Data from OCLC VIAF: D. H. Lawrence

Linked Data from Freebase: D. H. Lawrence

Linked Data from BBC: Programmes related to D. H. Lawrence

Archives Hub EAD data: D. H. Lawrence letters

Sindice/Sig.ma: RDF data aggregator/search

RDF & Linked Data: some strengths/features

• Designed for the Web, “open world”• Anyone can say anything about anything• No-one says everything about anything

• Extensible, decentralised• Rules for data merging/integration• Inferencing

RDF & Linked Data: Some challenges

New concepts, formats, tools (Re)modelling/migration/conversion Linking & identity Versioning & time Trust

How?

• Model our “world” • Design URI patterns• Select/create RDF vocabularies• Convert/transform data• Generate links• Publish/expose data

Acknowledgements / some useful sources

• Tom Heath & Chris Bizer, Linked Data: Evolving the Web into a Global Data Space http://linkeddatabook.com/

• Yves Raimond & Michael Smethurst, “A skim-read introduction to linked data”http://www.bbc.co.uk/blogs/radiolabs/s5/linked-data/s5.html

• Dave Reynolds, “Linked data and its role in the semantic web”http://www.slideshare.net/der42/introduction-to-linked-data-and-the-semantic-web-8700415

Linked DataA short(-ish) introductionBricolage Project meeting, Bristol, 26 Jan 2012

Pete Johnston Technical Researcher, [email protected]