Linked (Open) Data

Linked (Open) Data
Linked (Open) Data VU Web Engineering / TU Wien May 27th 2013 -‐ Bernhard Haslhofer -‐
About me •  Since 03/2013 Postdoc @ University of Vienna •  Previously –  Lecturer & Postdoc @ Cornell University, NY, USA –  Univ. Ass @ University of Vienna –  … –  WINF TU Wien 2003, INF TU Wien 2006 2
About me •  Research Interests – Web informaZon systems – Globally connected, Web-‐based data networks •  Structured Web Data (Linked Data, schema.org, (FB) Open Graph Protocol, etc.) •  Knowledge Graphs (e.g., DBpedia, Freebase) •  AnnotaZons / SemanZc Tagging •  Quality in Open Data Networks •  …. 3
My teaching philosophy •  A course is a collaboraZve experience •  Instructor provides –  Structure –  FoundaZon for learning •  Students –  Engage, contribute, challenge –  Ask quesZons! –  Think criZcally! –  Disagree if appropriate! 4 Aren’t we beyond that?
My plan for today… •  Linked (Open) Data ??? •  Linked Data – Intro & Overview •  Linked Data -‐ Technologies •  Recent Trends and Developments •  QuesZons / Discussion 5
Open Data “Open data is data that can be freely used, reused and redistributed by anyone -‐ subject only, at most, to the requirement to a:ribute and sharealike.” (Open Data Handbook, 2012, Open Knowledge FoundaZon) 6
“Open” Data DefiniZon •  Availability and Access –  Data must be available as a whole and at no more than a reasonable reproducZon cost, preferably by downloading over the internet –  Data must also be available in a convenient and modifiable form •  Reuse and RedistribuZon –  Data must be provided under terms that permit reuse and redistribuZon including the intermixing with other datasets. •  Universal ParZcipaZon –  Everyone must be able to use, reuse and redistribute (no discriminaZon) –  No ‘non-‐commercial’ restricZons (hip://opendefiniZon.org/okd/) 7
Open Data Movement 8 Source: http://www.flickr.com/photos/jamescridland/613445810/sizes/l/in/photo
QuesZons •  Why should the open data principles sound familiar to sokware engineers? •  Any known “open data” examples? 9
Open Government Data Examples 10
Open Government Data Apps 14
Open (Government) Data Apps 15
Open Government Data in Journalism 16
(Open) Data Journalism 17
Open Data in Science 18
Open Data in Science 19
Linked Data “A method of publishing structured data so that it can be interlinked and become more useful. It builds upon standard Web technologies such as HTTP, RDF and URIs, but rather than using them to serve web pages for human readers, it extends them to share informaLon in a way that can be read automaLcally by computers. This enables data from different sources to be connected and queried” [Bizer, Heath, Berners-‐Lee 2009] 20
Linked Open Data 21 Open Data + Linked Data = Linked Open Data
Linked Data context... http://www.youtube.com/watch?v=5Cb3ik6zP2I
Why Linked Data?
Why Linked Data?
Why Linked Data?
Web Architecture
Web Architecture •  A set of simple standards – Uniform global addressing (URI) – Uniform document encoding (HTML) – Uniform transportaZon (HTTP) •  Hyperlinks connecZng documents •  Works preiy well for accessing and exchanging documents
But someZmes we need to access the underlying structured data.
Web Services and Web APIs Source: http://www.blogperfume.com/new-27-circular-social-media-icons-in-3-sizes/
Web Services and Web APIs •  Each Web API has a proprietary interface •  Datasources must be known in advance •  InformaZon enZZes (papers, authors, subjects, etc.) are oken not linked
32 Social Networking Sites as Walled Gardens by David Simonds
Linked Data Vision •  Publish and link structured data on the Web •  Create a single globally connected data space based on the Web Architecture
Web of Linked Data •  A set of simple standards – Uniform global addressing (URI) – Uniform data model (RDF) – Uniform transportaZon (HTTP) •  RDF links connecZng enZZes •  Forms a global data space and facilitates accessing and exchanging data
What is Linked Data? •  A method to build a Web of Data •  Architectural style, set of standards
Linking Open Data Project •  A W3C community project with the goal to extend the Web with a data commons by publishing various open data sets as RDF on the Web and by serng links between data items from different sources
~$ curl -I -H "Accept: text/turtle" http://dbpedia.org/resource/The_Shining_(film) ~$ curl -H "Accept: text/turtle" http://dbpedia.org/data/The_Shining_(film).ttl ~$ sudo apt-get install raptor (Linux) ~$ brew install raptor (Mac OSX) ~$ rapper http://dbpedia.org/resource/The_Shining_(film)
Web / REST Basics -‐ Recap •  Key Architectural Web Components – IdenZficaZon: URI – InteracZon: HTTP – Standardized Document Formats: HTML, XML, JSON, etc. 51
Web / REST Basics -‐ Recap •  URIs idenZfy interesZng things – documents on the Web – relevant aspects of a data set – phone numbers, Skype usernames, e-‐mail addresses •  HTTP URIs name and address resources in Web-‐based systems 52
Web / REST Basics -‐ Recap •  A resource can have several representaZons •  RepresentaZons can be in any format –  HTML –  XML –  JSON –  … URI Resource Representation Plain Text text/plain http://example.com/someURI Representation HTML text/html Representation JSON text/json 53
Web / REST Basics -‐ Recap •  We deal with resource representaZons –  not the resources themselves (pass by value) –  representaZons can be in any format (defined by media-‐type) •  Each resource implements a standard uniform interface (HTTP) –  a small set of verbs applied to a large set of nouns –  verbs are universal and not invented on a per-‐applicaZon basis Client Server Logical Resources Physical Resources JSON Resource Representations Uniform Interface 54
Web / REST Basics -‐ Recap HTML, XHTML, ... XML, JSON, ... Transport and store data Display information 55
Web / REST Basics -‐ Recap •  Example Web Service operaZons: – Publish image on Flickr – Order a book at Amazon – Post a message on your friend’s Facebook wall – Update user photo on foursquare Web Application A Application B API 56
RDF •  A data model for represenZng data on the Web •  Several statements (triples) form a graph http://dbpedia.org/resource/ The_Shining_(film) The Shining (film) rdfs:label 闪灵 (电影) rdfs:label http://dbpedia.org/ontology/ Film rdf:type http://dbpedia.org/resource/ Jack_Nicholson dbpprop:starring http://xmlns.com/foaf/0.1/ Person rdf:type 1937-04-22 Jack Nicholson dbpedia-owl:birthDate foaf:name
RDF/XML, N3, Turtle, etc. •  Data formats for RDF resource representaZons •  Used to transfer RDF data between apps
RDFS •  A language for describing the syntax and semanZcs of schemas/vocabularies in a machine-‐understandable way http://dbpedia.org/ontology/ Film http://dbpedia.org/ontology/ Work rdfs:subClassOf
OWL •  A more expressive (formal) language for defining the syntax and semanZcs of schemas/vocabularies •  Solves RDFS shortcomings but introduces quite some complexity http://dbpedia.org/ontology/ starring http://www.w3.org/2002/07/ owl#ObjectProperty http://dbpedia.org/ontology/ Person http://dbpedia.org/ontology/ Work starring rdf:type rdfs:range rdfs:domain rdfs:label
SKOS •  A language for describing controlled vocabularies (taxonomies, thesauri, classificaZon schemes) http://dbpedia.org/resource/ The_Shining_(film) http://dbpedia.org/resource/ Category:1980s_horror_films http://dbpedia.org/resource/ Category:1980s_films http://www.w3.org/2004/02/ skos/core#Concept dcterms:subject rdf:type skos:broader rdf:type
SPARQL •  A query language and protocol for accessing RDF data on the Web SELECT DISTINCT ?x! WHERE {! !?x dcterms:subject ! !<http://dbpedia.org/resource/Category:1980s_horror_films> .! }!
Database Systems Analogy... Purpose Rela,onal Database Management Systems (RDBMS) Linked Data Technologies Query Schema DefiniZon Language Data RepresentaZon IdenZfiers 63 ?
Database Systems Analogy... Purpose Rela,onal Database Management Systems (RDBMS) Linked Data Technologies Query SQL SPARQL Schema DefiniZon Language SQL DDL RDFS / OWL Data RepresentaZon RelaZonal Model / Tables RDF / Graph IdenZfiers Primary Keys (numeric sequences) URI 64
Publishing Linked Data •  DisZnguish between non-‐informaZon and informaZon resource •  Sample non-‐informaZon resource –  hip://dbpedia.org/resource/The_Shining_(film) •  Sample informaZon resource –  hip://dbpedia.org/page/The_Shining_(film) -‐ HTML –  hip://dbpedia.org/data/The_Shining_(film) -‐ RDF
Publishing Linked Data GET http://dbpedia.org/resource/The_Shining_(film) Accept: application/rdf+xml 303 See Other Location: http://dbpedia.org/data/The_Shining_(film) GET http://dbpedia.org/data/The_Shining_(film) Accept: application/rdf+xml 200 OK ... <?xml version="1.0" encoding="utf-8"?> <rdf:RDF ...
Publishing Large RDF Datasets •  Run a servlet that implements the 303 publishing approach – for non informaZon resources •  parse Accept Header field •  Redirect (303 See Also) to corresponding informaZon resource •  Generate RDF SerializaZon dynamically from underlying data storage
Rich Snippets / Microdata 69
Microdata (HTML5) •  A very young HTML 5 proposiZon that extends Microformats and addresses its shortcomings •  Items are created within an itemscope •  Every item is assigned an arbitrary number of properZes (itemprop) and relaZonships (itemref) •  Uses global idenZfiers for typing and naming items
Microdata Example <div itemscope itemtype="http://schema.org/Person">! ! !<span itemprop="name">Bernhard Haslhofer</span>,! !<span itemprop="nickname">behas</span>. ! !<div !itemprop="address”! ! !itemscope itemtype="http://schema.org/PostalAddress">! ! !<span itemprop="streetAddress">301 College Avenue</span>! ! !<span itemprop=”addressLocality">Ithaca</span>! ! !<span itemprop=”addressCountry">United States</span>! !</div>! </div>!
Schema.org
schema.org / Microdata example <h1>Pirates of the Carribean: On Stranger Tides (2011)</h1>! Jack Sparrow and Barbossa embark on a quest to find the elusive fountain! of youth, only to discover that Blackbeard and his daughter are after it too.! ! Director: Rob Marshall! Writers: Ted Elliott, Terry Rossio, and 7 more credits! Stars: Johnny Depp, Penelope Cruz, Ian McShane! 8/10 stars from 200 users. Reviews: 50.!
schema.org / Microdata example
schema.org •  Defines – a number of types (e.g, person), organized in an inheritance hierarchy – a number of properZes (e.g., name) •  Extension mechanisms to extend the schemas •  OWL representaZon: hip://schema.org/docs/schemaorg.owl •  hip://schema.rdfs.org/index.html 76
Open Graph Protocol
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Google Knowledge Graph •  Enables search for things (people, places) that Google knows about •  Rooted in public sources such as Freebase, Wikipedia, CIA World Factbook, etc. – augmented to 500M objects, 3.5B facts and relaZonship •  Next generaZon search (semanZc index) 82
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Readings •  Tom Heath and ChrisZan Bizer (2011) Linked Data: Evolving the Web into a Global Data Space (1st ediZon). Synthesis Lectures on the SemanZc Web: Theory and Technology, 1:1, 1-‐136. Morgan & Claypool. •  Jason Ronallo: HTML5 Microdata and Schema.org hip://journal.code4lib.org/arZcles/6400

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