![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](https://image.slidesharecdn.com/vuwebengineeringtulinkedopendata-130606052410-phpapp01/85/Linked-Open-Data-20-320.jpg)
Linked (Open) Data
- 1. Linked (Open) Data VU Web Engineering / TU Wien May 27th 2013 -‐ Bernhard Haslhofer -‐
- 2. 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
- 3. 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
- 4. 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?
- 5. My plan for today… • Linked (Open) Data ??? • Linked Data – Intro & Overview • Linked Data -‐ Technologies • Recent Trends and Developments • QuesZons / Discussion 5
- 6. 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
- 7. “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
- 8. Open Data Movement 8 Source: http://www.flickr.com/photos/jamescridland/613445810/sizes/l/in/photo
- 9. QuesZons • Why should the open data principles sound familiar to sokware engineers? • Any known “open data” examples? 9
- 10. Open Government Data Examples 10
- 11. Open Government Data Examples 11
- 12. Open Government Data Examples 12
- 13. Open Government Data Examples 13
- 14. Open Government Data Apps 14
- 15. Open (Government) Data Apps 15
- 16. Open Government Data in Journalism 16
- 17. (Open) Data Journalism 17
- 18. Open Data in Science 18
- 19. Open Data in Science 19
- 20. 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
- 21. Linked Open Data 21 Open Data + Linked Data = Linked Open Data
- 22. My plan for today… • Linked (Open) Data ??? • Linked Data – Intro & Overview • Linked Data -‐ Technologies • Recent Trends and Developments • QuesZons / Discussion 22
- 23. Linked Data context... http://www.youtube.com/watch?v=5Cb3ik6zP2I
- 24. Why Linked Data?
- 25. Why Linked Data?
- 26. Why Linked Data?
- 27. Web Architecture
- 28. 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
- 29. But someZmes we need to access the underlying structured data.
- 30. Web Services and Web APIs Source: http://www.blogperfume.com/new-27-circular-social-media-icons-in-3-sizes/
- 31. 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. 32 Social Networking Sites as Walled Gardens by David Simonds
- 33. Linked Data Vision • Publish and link structured data on the Web • Create a single globally connected data space based on the Web Architecture
- 34. 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
- 35. What is Linked Data? • A method to build a Web of Data • Architectural style, set of standards
- 36. 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
- 42. ~$ 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)
- 50. My plan for today… • Linked (Open) Data ??? • Linked Data – Intro & Overview • Linked Data -‐ Technologies • Recent Trends and Developments • QuesZons / Discussion 50
- 51. Web / REST Basics -‐ Recap • Key Architectural Web Components – IdenZficaZon: URI – InteracZon: HTTP – Standardized Document Formats: HTML, XML, JSON, etc. 51
- 52. 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
- 53. 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
- 54. 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
- 55. Web / REST Basics -‐ Recap HTML, XHTML, ... XML, JSON, ... Transport and store data Display information 55
- 56. 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
- 57. 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
- 58. RDF/XML, N3, Turtle, etc. • Data formats for RDF resource representaZons • Used to transfer RDF data between apps
- 59. 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
- 60. 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
- 61. 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
- 62. 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> .! }!
- 63. Database Systems Analogy... Purpose Rela,onal Database Management Systems (RDBMS) Linked Data Technologies Query Schema DefiniZon Language Data RepresentaZon IdenZfiers 63 ?
- 64. 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
- 65. 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
- 66. 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 ...
- 67. 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
- 68. My plan for today… • Linked (Open) Data ??? • Linked Data – Intro & Overview • Linked Data -‐ Technologies • Recent Trends and Developments • QuesZons / Discussion 68
- 69. Rich Snippets / Microdata 69
- 70. 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
- 71. 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>!
- 72. Schema.org
- 74. 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.!
- 75. schema.org / Microdata example
- 76. 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
- 79. 79
- 82. 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
- 83. 83
- 84. 84
- 85. 85
- 86. 86
- 87. 87
- 88. 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