Linked Data and the Semantic Web: What Are They and Should I Care?

UKOLN is supported by: Linked Data and the Semantic Web - What are they and should I care? 6 th November 2009 UKOLN Staff Seminar, University of Bath, UK Adrian Stevenson

semantics is … devoted to the study of meaning … on the syntactic levels of words, phrases, sentences
http://en.wikipedia.org/wiki/Semantic

“ The Semantic Web is a web of data , in some ways like a global database” 1
“ first step is putting data on the Web in a form that machines can naturally understand... This creates what I call a Semantic Web - a web of data that can be processed directly or indirectly by machines” 2
1. http://www.w3.org/DesignIssues/Semantic.html
2. Tim Berners-Lee, Weaving the Web . Harper, San Francisco. 1999.

“ The term Linked Data refers to a set of best practices for publishing and connecting structured data on the Web.”
“ the Semantic Web is the goal or end result… Linked Data provides the means to reach that goal”
From ‘ Linked Data: The Story So Far ’ - Heath, Bizer and Berners-Lee 2009

The Web We’re Used To
Made by humans for humans
Primarily documents
Machines not very welcome
Data silos

Web of Linked Data
In 1998 the idea from Tim Berners-Lee of ‘linked data’ took shape
Designed for machines first
It primarily links data about ‘things’, not documents
… but it is for humans in the end

But haven’t we been putting data on the web for years?
In CSV , relational databases, XML etc?
Well yes, but these approaches are not so easy to integrate
Web 2.0 mashups work against a fixed set of data sources
Linked Data applications operate on top of an unbound, global data space.

So what’s happening now?

“ Sir Tim Berners-Lee, the inventor of the world wide web, will help the British government to make its data more easily available online … I have asked Sir Tim Berners-Lee … to help us drive the opening up of access to Government data in the web” Prime Minister Gordon Brown, 10 th June 2009
"What you find if you deal with people in government departments is that they hug their database, hold it really close”. Tim Berners-Lee, 10 th June 2009
We shall see …

data.gov.uk

BBC Music BETA

A little bit of the techy stuff

Linked Data is …
A way of publishing data on the web that:
Encourages reuse
Reduces redundancy
Maximises inter-connectedness
Enables network effects
So how is this achieved?

Presentational tagging – HTML
<h1>Agilitas Physiotherapy Centre</h1> <p>Welcome to the Agilitas Physiotherapy Centre home page. Do you feel pain? Have you had an injury? Let our staff Lisa Davenport, our secretary Kelly Townsend, and Steve Matthews take care of your body and soul.</p> <h2>Consultation hours</h2> Mon 11am - 7pm<br/> Tue 11am - 7pm<br/> Wed 3pm - 7pm<br/> Thu 11am - 7pm<br/> Fri 11am - 3pm
<p> But note that we do not offer consultation during the weeks of the <a href=". . .">State Of Origin</a> games.</p>

Semantic tagging
<company>
<treatmentOffered>Physiotherapy</treatmentOffered>
<companyName>Agilitas Physiotherapy Centre</companyName>
<staff>
<therapist>Lisa Davenport</therapist> <therapist>Steve Matthews</therapist>
<secretary>Kelly Townsend</secretary>
</staff>
</company>

Tim BL’s Linked Data Design Issues
Use URIs as names for things
Use HTTP URIs so that people can look up those names.
When someone looks up a URI, provide useful information, using the standards (RDF, SPARQL)
Include links to other URIs so that they can discover more things.
From http://www.w3.org/DesignIssues/LinkedData.html

URIs and HTTP
A “Uniform Resource Identifier (URI) provides a simple and extensible means for identifying a resource –RFC 3986
A URL is a type of URI
HTTP URIs can be ‘de-referenced’
HTTP URIs are used for “real world” things
http://adrianstevenson.com/id/me
http://dbpedia.org/page/Tim_Berners-Lee

RDF
Resource Description Framework
“ a language for representing information about resources in the World Wide Web”
“ RDF can also be used to represent information about things that can be identified on the Web, even when they cannot be directly retrieved on the Web”
Describes relations based on triples
S ubject-object-predicate
http://www.w3.org/TR/REC-rdf-syntax/

Heroes
has a
creator
whose name is
David Bowie
Subject Predicate Object

Linked Data in Use

Publishing Linked Data
RDFizers – convert data formats into RDF
D2R Server – creates linked data from relational databases
SparqPlug – Extracts linked data from HTML
… . Many others

Linked Data Applications
Linked Data Browsers – navigate between data sources
Disco
Tabulator
Marbles
Linked Data Search Engines
For humans – Falcons, SWSE
For apps – Swoogle, Sindice

Tracks provenance of data
Merges data about the same thing from different sources

User can explore the underlying data structures
Can search for objects, concepts or documents

Provides interface (API) that other linked data apps can use
Rationale: new linked data apps shouldn’t need to implement their own infrastructure for crawling and indexing web of data

Some issues
To RDF or not to RDF
Usability
Sustainability
Provenance
Licensing
Reliability

I Linked Data Therefore I RDF

Sustainability
Ed Summers at the Library of Congress created http://lcsh.info
Linked Data interface for LOC subject headings
People started using it

Library of Congress Subject Headings

Data Licensing
RDF Book Mashup
makes information about books, their authors, reviews, and online bookstores available on the Semantic Web
Uses Amazon Web Services but contravenes terms and conditions

Provenance
OK if data ‘watermarked’
But can often be a problem
VOID can help (apparently!)

Woolyish conclusion
Some interesting recent developments and sense of momentum
Central Gov’t interested
… but still much to do if the semantic web and linked data are to really take hold

Questions?
http://www.twitter.com/adrianstevenson
[email_address]

CC Attribution
Some sections of this presentation adapted from:
An Introduction to Linked Data , by Tom Heath
The Semantic Web – An Introduction by Owen Stephens
Using Linked Data as a Learning Resource Recommendation System by Chris Clarke
This presentation available under creative commons Noncommercial-Share Alike

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Linked Data and the Semantic Web: What Are They and Should I Care?

by Adrian Stevenson

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Linked Data and the Semantic Web: What Are They and Should I Care? Presentation Transcript