Michalis Vafopoulos NTUA, GFOSS & The transformers GREEN CITY HACKATHON

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Michalis Vafopoulos NTUA, GFOSS & www.publicspending.net The transformersGREEN CITY HACKATHON






6Welcome to the data era

7Data: Open, big, linkedOpen: accesseveryone to use and republish as she wishes

Big: scalehigh volume, velocity and variety

Linked: usePublish once, use as many times

8How is it working?Linked data in a nutshell

Sources: T. Heath, J. Sequeda, the Web

9The Web of DocumentsAnalogy: a global file systemDesigned for: human consumptionPrimary objects: documentsLinks between: documents (or sub-parts of)Degree of structure in objects: fairly lowSemantics of content and links: implicit-humans(Tom Heath)

The web = the internet + links + documents

10The Web of DocumentsSimple, big and unstructuredOrganized in Silos

But humans are interested in:Things, no documents andthese Things might be in documents or elsewhere

11The Web of DataAnalogy: a global filesystem ----> global databaseDesigned for:human consumption ->machines first-humans laterPrimary objects: documents --> things (or descriptions of things)Links between: documents --> things Degree of structure in objects: fairly low ---> highSemantics of content and links: implicit --> explicit(Tom Heath)


12The Web of Data: why?13

encourages reuse reduces redundancy maximises its (real and potential) inter-connectedness enables network effects to add value to data13The Web of Data: how?14Current state on the WebRelational DatabasesAPIsXMLCSVXLS

Computers cant consume data because:Different formats & modelsNot inter-connected

14The Web of Data: how?15 we need to create a standard way of publishing Data on the Web (like HTML for docs)

This is the Resource Description Framework (RDF)

15Resource Description Framework (RDF)A data model A way to model dataInspired form Relational databases and LogicRDF is a triple data modelLabeled Graph (semantic networks)Subject, Predicate, Object Example: Document on the Web

Databases back up documentsIsbnTitleAuthorPublisherIDReleasedData978-0-596-15381-6Programming the Semantic WebToby Segaran1July 2009PublisherIDPublisherName1OReilly MediaThis is a THING:A book title Programming the Semantic Web by Toby Segaran, THINGS have PROPERTIES:A Book as a Title, an author, Data representation in RDFbookProgramming the Semantic Web978-0-596-15381-6Toby Segaran PublisherOReillytitlenameauthorpublisherisbnIsbnTitleAuthorPublisherIDReleasedData978-0-596-15381-6Programming the Semantic WebToby Segaran1July 2009PublisherIDPublisherName1OReilly MediaEverything on the web is identified by a URI!

link the data to other datahttp:///isbn978Programming the Semantic Web978-0-596-15381-6Toby Segaran http:///publisher1OReillytitlenameauthorpublisherisbnconsider the data from Revyu.comhttp:///isbn978http:///review1Awesome Bookhttp:///reviewerJuan SequedahasReviewreviewerdescriptionnamestart to link datahttp://isbn978Programming the Semantic Web978-0-596-15381-6Toby Segaran http://publisher1OReillytitlenameauthorpublisherisbnhttp://isbn978sameAshttp://review1Awesome Bookhttp://reviewerJuan SequedahasReviewhasReviewerdescriptionnameJuan Sequeda publishes data toohttp://juansequeda.com/idlivesInJuan Sequedanamehttp://dbpedia.org/AustinLets link more datahttp:///isbn978http:///review1Awesome Bookhttp:///reviewerJuan Sequedahttp://juansequeda.com/idhasReviewhasReviewerdescriptionnamesameAslivesInJuan Sequedanamehttp://dbpedia.org/AustinAnd morehttp:///isbn978Programming the Semantic Web978-0-596-15381-6Toby Segaran http:///publisher1OReillytitlenameauthorpublisherisbnhttp:///isbn978sameAshttp:///review1Awesome Bookhttp:///reviewerJuan Sequedahttp://juansequeda.com/idhasReviewhasReviewerdescriptionnamesameAslivesInJuan Sequedanamehttp://dbpedia.org/AustinLinked data = internet + http + RDFLinked Data PrinciplesUse URIs as names for thingsUse URIs so that people can look up (dereference) those names.When someone looks up a URI, provide useful information.Include links to other URIs so that they can discover more things.Web as a databaseLinked Data makes the web exploitable as ONE GIANT HUGE GLOBAL DATABASE!

Is there any query language like sql?SPARQL

The LOD cloud: May 2007

What is a Linked Data application/service?Software system that makes use of data on the Web from multiple datasets and that benefits from links between the datasets

Characteristics of Linked Data Applications IConsume data that is published on the web following the Linked Data principles: an application should be able to request, retrieve and process the accessed data

Discover further information by following the links between different data sources

Characteristics of Linked Data Applications IICombine the consumed linked data with data from sources (not necessarily Linked Data) Expose the combined data back to the web following the Linked Data principles

Offer value to end-users

the 5 stars of open linked datamake your stuff available on the Web (whatever format)make it available as structured data (e.g. excel instead of image scan of a table)non-proprietary format (e.g. csv instead of excel)use URLs to identify things, so that people can point at your stufflink your data to other peoples data to provide context

http://lab.linkeddata.deri.ie/2010/star-scheme-by-example/ Ideas for projectsThink of interesting questions Search for related datasets

And start playing with:Interconnections links to other datasets Statistical analysisEconomic/business analysis


36More examplesCurrent Employee Names, Salaries, and Position TitlesThe Open Database Of The Corporate WorldCrime mapNHS efficiency savings: the role of prescribing analyticswhere public money goes worldwide

37More infoTwitter: @vafopoulosVafopoulos@gmail.comwww.Vafopoulos.org www.publicspending.net www.Youtube.com/websciencegr