1. Web of Data in the Context of Multimedia
Part 1: Linked Open Data: Vision, Concepts and Technologies
Bernhard Haslhofer, Bernhard Schandl, Andreas Langegger,
Wolfgang Halb, Tobias Bürger
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2. Agenda
Introduction Multimedia Interlinking
Producing Linked Data Multimedia Annotations
Existing Data Sets Enriching Personal
Media Collections
Linking Data
Consuming Linked Data
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3. Introduction: The Web of Data Vision
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8. Web of Data Vision
There is lots of data about the movie “The Shining”
available on the Web…
Genre: Horror/Thriller Release Date: 23 May
1980 (USA)
Title: The Shining Distributors: Warner Bros. Pictures Distribution
Running Time: 146 min (original), 144 min (cut),
120min (European cut)
Starring: Jack
Nicholson, Shelly Produced by: Stanley Kubrick
Duvall, Danny Lloyd, …
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9. Web of Data Vision
…but only in a human-readable representation
(HTML)
Difficult to access these data by applications, unless
they start parsing HTML representations (difficult, erroneous)
they use data source specific APIs (e.g., Web Services), if there
are any
Metadata about (multimedia) resources are still
locked in closed data silos
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10. DB DB
DB DB
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11. Web of Data Vision
The Web is successful because it provides
Uniform encoding (HTML)
Uniform addressing (URI)
Uniform transportation (HTTP)
for the exchange of documents.
Why not apply the same mechanism to the
underlying data?
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12. Web of Data Vision
The Web of Data vision is to use the Web to provide
access not only to documents but also to the
underlying data
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13. The Linked Data Principles
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
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14. The Enabling Technologies
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15. URI
Uniform Resource Identifiers (URI) identify things
Use dereferencable HTTP URIs in the Web of Data
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16. RDF
A data model for representing metadata on the Web
Several statements (triples) form a graph
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17. RDF
Links are an intrinsic RDF feature
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18. RDF/XML, N3, Turtle, etc
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19. RDFS
A language for describing vocabularies in a machine-
understandable way
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20. OWL
A more expressive language for expressing
vocabularies and/or ontologies in a machine-
understandable way
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21. SKOS
A language for describing controlled vocabularies
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22. SPARQL
A query language and protocol for accessing RDF
data on the Web
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23. Linked Data Implementation Best
Practices
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24. How to publish vocabularies
Hash-based URIs
E.g., http://example.com/example1#ClassA
Suited to group the description of a moderate number of related
terms into one document
Agent can retrieve terms with a single HTTP request
Slash-based URIs
E.g., http://example.com/example1/ClassB
Suited to split the descriptions of terms in large vocabularies into
one document per term
No need for the agent to download a massive document to find
the description of a term
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25. How to publish vocabularies
E.g.. extended configuration for hash namespace
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26. How to publish vocabularies
E.g.. extended configuration for hash namespace
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27. How to publish Linked Data
Distinguish between
non-information resource
http://dbpedia.org/resource/The_Shining_%28film%29
Information resource
http://dbpedia.org/page/The_Shining_%28film%29 (HTML)
http://dbpedia.org/data/The_Shining_%28film%29 (RDF)
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28. The Linking Open Data Project
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29. Some clarifications
Open Data: a philosophy, practice, or policy that data
are freely available to everyone without restrictions
from copyright, patents, a.s.o.
Linked Data: best practices for exposing, sharing,
and connecting data using URIs and RDF
Linking Open Data: 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 setting links between data items from
different sources
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30. As of October 2007
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33. Available Tools - Overview
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34. RDF APIs
Jena Semantic Web Framework (Java)
http://jena.sourceforge.net/
Sesame
ARC (PhP)
http://arc.semsol.org/
Redland RDF – Ruby interface (Ruby)
http://librdf.org/docs/ruby.html
RDFlib (Python)
http://www.rdflib.net/
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35. Triple Stores
Jena Semantic Web Framework (Java)
http://jena.sourceforge.net
Sesame (Java)
http://www.openrdf.org/
OpenLink Virtuoso
http://virtuoso.openlinksw.com/dataspace/dav/wiki/Main/
ARC (PhP)
http://arc.semsol.org/
…
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36. References
RDF Primer: http://www.w3.org/TR/rdf-primer/
OWL 2 Overview:
http://www.w3.org/TR/2009/REC-owl2-
primer-20091027/
Best Practice Recipes for Publishing RDF
Vocabularies:
http://www.w3.org/TR/swbp-vocab-pub/
How to Publish Linked Data on the Web:
http://www4.wiwiss.fu-berlin.de/bizer/pub/
LinkedDataTutorial/
Pedantic Web Group: http://pedantic-web.org/
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37. References
Linking Open Data Project
http://esw.w3.org/topic/SweoIG/TaskForces/CommunityProjects/
LinkingOpenData
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38. Agenda
Introduction Multimedia Interlinking
Producing Linked Data Multimedia Annotations
Existing Data Sets Enriching Personal
Media Collections
Linking Data
Consuming Linked Data
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39. Linked Data Publishing Steps
The basic tenets of Linked Data are to:
use the RDF data model to publish structured data
on the Web
use RDF links to interlink data from different data
sources
RDF data can be contained in
a single file (RDF/XML) or
embedded in an existing file with RDFa
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40. Principles
Resources
all items of interest are called resources
Resource Identifiers
Uniform Resource Identifiers (URIs) are used, use of
HTTP URIs is strongly suggested
Representation
of an information resource is a stream of bytes
(HTML, JPG, RDF, …)
Dereferencing HTTP URIs
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41. Content Negotiation
Example:
http://dbpedia.org/resource/Graz
(URI identifying the non-information resource Graz)
http://dbpedia.org/data/Graz (information resource with an RDF/
XML representation describing Graz)
http://dbpedia.org/page/Graz (information resource with an HTML
representation describing Graz)
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42. Content Negotiation with RDFa
When RDF is embedded in another representation
(e.g. via RDFa) no content negotiation is needed
One representation is used for both humans and
machines
(X)HTML
RDF
XHTML+RDFa representation
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43. RDFa example
Plain (X)HTML:
... All content on this site is licensed under
<a href="http://creativecommons.org/licenses/by/3.0/">
a Creative Commons License </a>.
(X)HTML with RDF embedded:
... All content on this site is licensed under
<a rel="license“ href="http://creativecommons.org/licenses/by/
3.0/">
a Creative Commons License </a>.
More information on RDFa:
http://www.w3.org/TR/xhtml-rdfa-primer/
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44. Choosing URIs
Resources are named with URI references
Choose „good“ URIs for your resources
Cool URIs for the Semantic Web
http://www.w3.org/TR/cooluris/
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45. Choosing URIs
Use HTTP URIs for everything
Define your URIs in an HTTP namespace under your
control
Keep implementation details out of your URIs.
Short, mnemonic names are better
http://dbpedia.org/resource/Graz VS
http://www.confuseme.com:2020/demos/xyz/cgi-bin/
resources.php?id=Graz
Try to keep your URIs stable and persistent
Cool URIs don’t change!
Use some kind of primary key inside your URIs
(e.g. when dealing with books use the ISBN, etc.)
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46. Which vocabularies to use?
Reuse terms from well-known vocabularies wherever
possible
Only define new terms yourself if you can’t find
required terms in existing vocabularies
List of well-known vocabularies:
http://esw.w3.org/topic/TaskForces/Community
Projects/LinkingOpenData/CommonVocabularies
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47. Some well-known vocabularies
Friend-of-a-Friend (FOAF), vocabulary for describing
people.
Dublin Core (DC) defines general metadata attributes.
Semantically-Interlinked Online Communities (SIOC),
vocabulary for representing online communities.
Description of a Project (DOAP), vocabulary for describing
projects.
Simple Knowledge Organization System (SKOS),
vocabulary for representing taxonomies and loosely
structured knowledge.
Music Ontology provides terms for describing artists,
albums and tracks.
Review Vocabulary, vocabulary for representing reviews.
Creative Commons (CC), vocabulary for describing
license terms.
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48. More best practices
You can mix terms from different vocabularies, e.g.
rdfs:label and foaf:depiction
Use URI references from well-established data
sources, e.g.:
Geonames
DBpedia
MusicBrainz
RDF Book Mashup
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49. Defining your own terms
If you need to define own terms use RDFS or OWL.
1. Do not define new vocabularies from scratch
2. Provide for both humans and machines
3. Make term URIs dereferenceable
4. Make use of other people's terms
5. State all important information explicitly
6. Do not create over-constrained, brittle models;
leave some flexibility for growth
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50. What should the RDF contain?
What triples should go into the RDF representation that
is returned (after a 303 redirect) in response to
dereferencing a URI identifying a non-information
resource?
Description
Backlinks
(Related descriptions)
Metadata
Syntax: RDF/XML (+ maybe other serializations)
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51. Serving linked data
Things must be identified with dereferenceable HTTP
URIs
When MIME-type application/rdf+xml is requested, a
data source must return an RDF/XML description of
the identified resource
Provide RDF links to other resources so that clients
can navigate the Web of Data by following RDF links
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52. Serving static RDF files
RDF files generated manually or
generated by some software
Configure server for correct MIME types
When using Apache and server is not yet configured to return the
correct MIME type add to httpd.conf or .htaccess:
AddType application/rdf+xml .rdf
File size (should be < 1 MB)
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53. Serving relational databases
Several tools exist to generate RDF from relational
databases
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54. Linked Data Publishing Steps
For more information:
Tutorial „How to Publish Linked Data on the Web”
By Chris Bizer, Richard Cyganiak, Tom Heath
http://www4.wiwiss.fu-berlin.de/bizer/pub/LinkedDataTutorial/
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55. RDB2RDF
W3C Incubator Group in 2008 & early 2009 to
examine existing approaches for generating RDF
from relational databases
http://www.w3.org/2005/Incubator/rdb2rdf/
Survey of Current Approaches for Mapping of Relational
Databases to RDF
http://www.w3.org/2005/Incubator/rdb2rdf/RDB2RDF_SurveyReport.pdf
Incubator Group Report
http://www.w3.org/2005/Incubator/rdb2rdf/XGR-rdb2rdf/
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56. RDB2RDF Working Group
W3C Working Group started in 2009 to standardize
a language for mapping relational data and relational
database schemas into RDF and OWL, tentatively
called the RDB2RDF Mapping Language, R2RML
http://www.w3.org/2001/sw/rdb2rdf/
First public results to be expected in early 2010
Participants from industry and academia
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57. Tools for Publishing Linked Data
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58. Pubby Linked Data Frontend
Provides Linked Data from SPARQL endpoint
data must be available in RDF already
if not: use a wrapper
Originally developed for DBpedia
Richard Cyganiak, Chris Bizer - FU Berlin
Provides dereferenceable HTTP-URIs
Simple HTML interface for browsing
Handles 303 redirects correctly
Content Negotiation (HTML, RDF/XML, N3)
Java Web application
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59. Pubby - Architecture
Text
Text
SPARQL endpoint must support DESCRIBE queries
supports multiple datasets (SPARQL endpoints)
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60. Pubby Setup How-To
Download and extract from:
http://www4.wiwiss.fu-berlin.de/pubby/download
Setup a Servlet Container (e.g. Tomcat, Jetty...)
Use ant to build WAR or copy /webapp folder
Configure
config file in WEB-INF/config.n3
file location can be set by context param. “config-file” in web.xml
N3 syntax
General Server section (instance of conf:Configuration)
conf:webBase - root of URL of web application, e.g. http://localhost/
sub-section for each dataset
conf:sparqlEndpoint - SPARQL endpoint URI
conf:datasetBase - common URI prefix of resources in the dataset
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61. Wrapping Relational Databases
D2RQ-Map and D2R-Server (FU Berlin)
http://sites.wiwiss.fu-berlin.de/suhl/bizer/d2r-server/index.html)
Triplify (Uni Leipzig)
http://triplify.org)
OpenLink Virtuoso RDF Views
http://virtuoso.openlinksw.com/wiki/main/Main/
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62. D2RQ-Map and D2R-Server
Java
wraps any ODBC database to RDF
2 Components
D2RQ-Map (wrapping component): dumps + virtual
D2R-Server (adds SPARQL endpoint)
can be used in Jena applications (Assembler)
Automatic generation of mapping file (simple)
shell script: “generate-mapping”
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63. D2RQ-Map and D2R-Server
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64. D2R-Server How-To
Download/Extract
Generate mapping file automatically first
generate-mapping -o mapping.n3 -d driver.class.name!
-u db-user -p db-password jdbc:url:..."
Inspect the generated mapping
Model your desired target graph
you should always know what you want...
also study your source database model
Adjust the mapping
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65. Mapping language
d2rq:Database
d2rq:ClassMap
d2rq:PropertyBridge
Rather expressive
Joins
Conditions
Value-translations
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66. Example Mapping
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67. Wrapping Spreadsheets
Excel2RDF, RDF123, TopBraid Composer
XLWrap (A. Langegger)
http://xlwrap.sourceforge.net/
supports cross tables, repetitive patterns in spreadsheets
arbitrary target graphs
powerful expressions (extensible, user-defined functions)
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68. XLWrap Example
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69. Example Template Graph
§ [ xl:uri "'http://example.org/revenue_' &!
§ URLENCODE(SHEETNAME(A1) & '_' & B2 & '_' &!
§ A4)"^^xl:Expr ] a ex:Revenue ;!
§ ex:country "DBP_LOCALITY(SHEETNAME(A1))"^^xl:Expr ;!
§ ex:year "DBP_YEAR(B2)"^^xl:Expr ;!
§ ex:product "A4"^^xl:Expr ;!
§ ex:itemsSold "B4"^^xl:Expr ;!
Text
§ ex:revenue "C4"^^xl:Expr .!
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70. Agenda
Introduction Multimedia Interlinking
Producing Linked Data Multimedia Annotations
Existing Data Sets Enriching Personal
Media Collections
Linking Data
Consuming Linked Data
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71. Existing Relevant
Linked Data Sets
What is out there?
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72. The Linked Data Cloud
(a success story, 2007-2009)
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74. 74 SAMT 2009 – Tutorial Web of Data in the Context of Multimedia (WoDMM) 10/2007
Graz, Austria - 2 Dec 2009
75. 75 SAMT 2009 – Tutorial Web of Data in the Context of Multimedia (WoDMM) 03/2008
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79. Some numbers
Data Set # of RDF Triples
ACM RKB > 12,000,000
AudioScrobbler > 600,000,000
BBC Music + Programmes > 20,000,000
Bio2RDF > 2,000,000,000
data.gov > 5,000,000,000
DBpedia > 470,000,000
Freebase > 100,000,000
Geonames > 90,000,000
Linked Geo Data > 3,000,000,000
MusicBrainz > 60,000,000
RDF Book Mashup > 100,000,000
US Census Data > 1,000,000,000
Source: http://esw.w3.org/topic/TaskForces/CommunityProjects/LinkingOpenData/DataSets/Statistics
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80. DBpedia: the Linked Data Hub
DBpedia [Auer07] is a Linked Data representation of
Wikipedia content.
(Semi-)structured data are extracted (mostly from
infoboxes) and are published as RDF.
DBpedia 3.4 (Nov. 2009) describes 2.9 million things,
including persons, places, organizations, ...
Each thing has an URI; most of them have a label
and an abstract, in up to 91 languages.
DBpedia provides > 8 millions links to other data sets
(web pages and RDF), and 75,000 YAGO
categories.
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81. DBpedia Vocabularies
DBpedia uses its own set of terms, which are
derived from the naming in Wikipedia Infoboxes.
Additionally used: RDF standard terms, FOAF.
The importance of DBpedia lies not primarily in the
data it provides, but in the names (i.e., HTTP
URIs) it provides.
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84. BBC Linked Data
BBC is continually increasing their Linked Data
services.
BBC Programmes publishes all broadcast
programmes and provides URIs for them.
BBC Music provides data about music artists and
links to DBpedia and MusicBrainz.
BBC uses Linked Data technology to link their
internal, heterogeneous data sets [Kobi09].
Used vocabularies: RDF(S), FOAF, DC, Music
Ontology, ...
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87. DBtune
DBtune [Rai08] is a collection of music-related
Linked Data sets, amongst others:
Jamendo (creative commons music site)
MusicBrainz (community music metadata)
AudioScrobbler (last.fm playcounts)
MySpace
URIs for entities can be retrieved by lookup services
or through links to DBpedia and other data sets.
Used vocabularies: RDF(S), FOAF, DC, Music
Ontology, ...
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90. Linked Movie Data Base
LMDB [Hass09] is an RDF representation of parts of
the data from the Internet Movie Database (IMDb).
Data about ~40,000 films, ~30,000 actors, ~8,000
directors, etc.
Links to
DBpedia
YAGO
flickr
RDF book mashup
MusicBrainz
Geonames
Vocabularies: RDF(S), FOAF, Movie Ontology,
SKOS, DC
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93. There is more ...
flickr wrapper: generates links to flickr pictures on
demand, represents them as RDF
Geonames: information about places (cities,
countries)
Linked Geo Data: RDF representation of
OpenStreetMap (geo data)
revyu.com: provides reviews for any kind of entities
(including movies and music)
New York Times: >5.000 concepts from their archive
and many more ...
Data is out there ... use it!
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94. References & Credits
The Linked Data Cloud is maintained by Richard
Cyganiak and Anja Jentzsch.
[Auer07] S. Auer et al., DBpedia: A Nucleus for a
Web of Open Data, Proc. ISWC 2007
[Kobi09] G. Kobilarov et al., Media Meets Semantic
Web – How the BBC Uses DBpedia and Linked Data
to Make Connections, Proc. ESWC 2009
[Rai08] Y. Raimond et al., A Web of Musical
Information, Proc. ISMIR 2008
[Hass09] O. Hassanzadeh et al., Linked Movie Data
Base, Proc. LDOW 2009
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95. Web of Data in the Context of Multimedia
Part 1: Linked Open Data: Vision, Concepts and Technologies
Linking Data
Bernhard Haslhofer, Bernhard Schandl, Andreas Langegger,
Wolfgang Halb, Tobias Bürger
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96. Linking Data
RDF links enable Linked Data browsers and crawlers
to navigate between data sources and to discover
additional data.
Properties used to link data depend on the
application domain, e.g.
:person1 foaf:knows :person2
Use owl:sameAs for URI aliases when two URIs refer
to the same thing
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97. Linking Data
Example: Equivalent URIs for
http://data.linkedmdb.org/resource/film/2014
owl:sameAs
1.http://dbpedia.org/resource/The_Shining_(film)
2.http://data.linkedmdb.org/resource/film/2014
3.
http://rdf.freebase.com/ns/guid.
9202a8c04000641f800000000046c3da
Linking can be de done
manually
automatically
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98. Setting RDF links manually
Usually only done in very small datasets like
personal FOAF profiles (e.g. stating who you know
by setting foaf:knows links)
Look up URI for the resource that you want to link to
uriqr.com
sindice.com
(SPARQL) queries to existing datasets
Use the URI identifying the resource,
http://dbpedia.org/resource/The_Shining_(film)
not the URI for the document about it
http://dbpedia.org/page/The_Shining_(film)
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99. Auto-generating RDF links
Manual approach not feasible for larger datasets
Record linkage well-known problem in the DB world
Specialised pattern-based algorithms for individual
problems
Use of unique identifiers (e.g. ISBN for books, ISIN for financial
securites, ISO-3166 country codes, etc.)
Example:
http://dbpedia.org/resource/Harry_Potter_and_the_Half-Blood_Prince
has a property dbpprop:isbn 747581088
owl:sameAs link can be easily generated to
http://www4.wiwiss.fu-berlin.de/bookmashup/books/0747581088
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100. Tools for data interlinking
Input: 2 (or more) datasets + linkage specification
Output: links between the datasets
Domain-independent tools:
SILK
ODD-Linker
RDF-AI
Knofuss
Domain-specific tools:
LD-Mapper (Music Ontology)
RKB co-reference resolution system (publications)
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101. Overview
RKB CRS LD-Mapper ODD RDF-AI Silk Knofuss
Ontologies multi multi single single single multi
Automation semi automatic semi semi semi semi
dataset structure links spec.
alignment alignment merged
User input ad-hoc program none link spec. query method method ontology
Silk-LSL
Input format Java Prolog LinQL XML (XML) OWL
Matching string, similarity string, adaptive
techniques string propagation string, Wordnet string string learning
Onto. alignment no no no no no yes, as input
alignment alignment
owl:sameAs format, merged format, merged
Output owl:sameAs linkset linkset dataset linkset dataset
Data access API local copy ODBC local copy SPARQL local copy
Domain publications Music Ontology independent independent independent independent
Overview generated by François Scharffe and Jérôme Euzenat
http://melinda.inrialpes.fr
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102. Specification formats
datasets resources links matching
SPARQL endpoint, resources to interlink, link condition (for string matching,
Silk-LSL graphs name resources type each resource) matchers combination
string matching (for
Knowfuss local copy (SPARQL query) fusion method each resource)
RDF-AI local copy resource descriptions link description fuzzy string, wordnet
LD-Mapper local copy resource query link description string matching
synonym, hyponym,
resource description weightedJaccard,
ODD-linker local copy (table.column) link description, token intersect
Overview generated by François Scharffe and Jérôme Euzenat
http://melinda.inrialpes.fr
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103. SILK
Silk - A Linking Framework for the Web of Data
http://www4.wiwiss.fu-berlin.de/bizer/silk/
Silk Link Specification Language
User specifies the type of resources to be linked and
the comparison technique to be used
Silk uses many string comparison techniques,
numerical and date similarity measures, concept
distances in a taxonomy
103 SAMT 2009 – Tutorial Web of Data in the Context of Multimedia (WoDMM) Graz, Austria - 2 Dec 2009
104. SILK
Input: 2 datasets behind SPARQL endpoint + LSL
specification
Output: linkset with owl:sameAs (or other user
specified property) links between resources
Silk LSL example on next slide
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105. <Interlink id="cities">
<LinkType>owl:sameAs</LinkType>
<SourceDataset dataSource="dbpedia" var="a">
<RestrictTo>
?a rdf:type dbpedia:City
</RestrictTo>
</SourceDataset>
<TargetDataset dataSource="geonames" var="b">
<RestrictTo>
?b rdf:type gn:P
</RestrictTo>
</TargetDataset>
<LinkCondition>
<AVG>
<Compare metric="jaroSimilarity">
<Param name="str1" path="?a/rdfs:label" />
<Param name="str2" path="?b/gn:name" />
</Compare>
<Compare metric="numSimilarity">
<Param name="num1" path="?city1/dbpedia:populationTotal" />
<Param name="num2" path="?city2/gn:population" />
<Compare>
</AVG>
</LinkCondition>
<Thresholds accept="0.9" verify="0.7" />
<Output acceptedLinks="accepted_links.n3"
verifyLinks="verify_links.n3"
mode="truncate" />
</Interlink>
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106. Web of Data in the Context of Multimedia
Part 1: Linked Open Data: Vision, Concepts, and Technologies:
Consuming Linked Data
Bernhard Haslhofer, Bernhard Schandl, Andreas Langegger,
Wolfgang Halb, Tobias Bürger
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107. Agenda
URI Discovery
Data Discovery
Data Set Discovery
Tools and Libraries to Access and Consume Linked
Data
Mashups and Browsers
Programmatic Access to Linked Data
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108. URI Discovery
1. Querying specific data sources,
e.g., http://lookup.dbpedia.org
2. Using dedicated search engines,
e.g.,
Falcons
http://iws.seu.edu.cn/services/falcons/
Sindice
http://sindice.com
SWSE
http://www.swse.org
Watson
http://watson.kmi.open.ac.uk
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109. Example Search Engine:
Falcons
(1) Entry of keywords
(2) Results of objects
(3) Class hierarchy to refine search
Try yourself: http://iws.seu.edu.cn/services/falcons/
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110. Data Discovery
1. Manual link traveral (i.e. follow rdfs:seeAlso or
owl:sameAs links)
2. Use of co-reference services, e.g. http://sameas.org
3. Use of Uri-based query engines, e.g.
http://sindice.org
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111. Sameas.org
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112. Sindice.org
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113. Data Set Discovery
1. Manually, i.e., by browsing and selecting a data set
from http://esw.w3.org/topic/SparqlEndpoints
2. (Semi-) automatically, i.e., by exploiting VoiD, the
Vocabulary of interlinked Datasets
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114. Describing Datasets
The problem:
Only human comprehensible descriptions of datasets available
Automation of tasks impossible such as
Efficient & effective search
Selection of datasets (for apps, interlinking targets)
Generation of maps, etc.
Solution: voiD, the “Vocabulary of Interlinked Datasets”
provides a formal description of
What a dataset is about (topic, technical details).
How and under which conditions to access it.
How the dataset is interlinked with other datasets.
Qualitative level: type of interlinking.
Quantitative level: number of links, resources, etc.
How to discover the metadata.
cf. K. Alexander, R. Cyganiak, M. Hausenblas, and J. Zhao "Describing Linked Datasets" Proceedings of LDOW 2009, 2009.
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115. VoiD – Core concepts
A dataset is a set of RDF triples that are published, maintained or
aggregated by a single provider.
A dataset is authoritative with respect to a certain URI namespace
if it contains information about resources named by URIs in this
namespace, and is published by the URI owner.
A linkset LS is a set of RDF triples where for all triples ti=
⟨si,pi,oi⟩ ∈ LS, the subject is in one dataset, i.e. all si are
described in DS1 , and the object is in another dataset, i.e. all oi are
described in DS2 .
cf. K. Alexander, R. Cyganiak, M. Hausenblas, and J. Zhao "Describing Linked Datasets" Proceedings of LDOW 2009, 2009.
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116. voiD Vocabulary
cf. K. Alexander, R. Cyganiak, M. Hausenblas, and J. Zhao "Describing Linked Datasets" Proceedings of LDOW 2009, 2009.
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117. voiD Usage Example
cf. K. Alexander, R. Cyganiak, M. Hausenblas, and J. Zhao "Describing Linked Datasets" Proceedings of LDOW 2009, 2009.
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118. Tools and Applications to
Consume Linked Data
Linked Data browsers
To explore things and datasets and to navigate between them.
Tabulator Browser (MIT, USA), Marbles (FU Berlin, DE), OpenLink RDF
Browser (OpenLink, UK), Zitgist Dataviewr (Zitgist, USA), Disco
Hyperdata Browser (FU Berlin, DE), Fenfire (DERI, Ireland)
Linked Data mashups
Sites that mash up (thus combine Linked data)
Revyu.com (KMI, UK), DBtune Slashfacet (Queen Mary, UK), DBPedia
Mobile (FU Berlin, DE), Semantic Web Pipes (DERI, Ireland)
Search engines
To search for Linked Data.
Falcons (IWS, China), Sindice (DERI, Ireland), MicroSearch (Yahoo,
Spain), Watson (Open University, UK), SWSE (DERI, Ireland), Swoogle
(UMBC, USA)
Listing on this slide by T. Heath, M. Hausenblas, C. Bizer, R. Cyganiak, O. Hartig
118 SAMT 2009 – Tutorial Web of Data in the Context of Multimedia (WoDMM) Graz, Austria - 2 Dec 2009
119. Example Linked Data Browser:
Marbles
Server-based Linked Data browser.
Formats RDF for XHTML using Fresnel.
Unique feature: Indicates the origin of displayed data
using colored dots.
Support for different views:
Full view: all available data is displayed.
Summary view: returns a short textual summary about a resource.
Photo view: provides a photo for a given resource.
Retrieves data from multiple sources by (a) issuing
parallel queries to multiple Linked Data search
engines and (b) by following owl:sameAs and
rdfs:seeAlso links.
119 SAMT 2009 – Tutorial Web of Data in the Context of Multimedia (WoDMM) Graz, Austria - 2 Dec 2009
120. Example Linked Data Browser:
Marbles (2) (1) Entry of query URL
(2) Data display
Try yourself: http://
marbles.sourceforge.net/
(3) Sources
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121. Example Linked Data Browser:
gFacet
cf. Heim, P., Ziegler, J., and Lohmann, S. "gFacet: A Browser for the Web of Data" In
Proceedings of IMC-SSW 2008, 2008. Try yourself: http://gFacet.org
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122. Example Mashup: Revyu.com
Picture from revyu.com
Try yourself: http://revyu.com
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123. Example Mashup: DBPedia
Mobile
Pictures from DBPedia Mobile
Try yourself: http://wiki.dbpedia.org/DBpediaMobile
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124. Libraries to Programmatically
Access the Web of Data
SPARQL JavaScript Library,
http://www.thefigtrees.net/lee/blog/2006/04/
sparql_calendar_demo_a_sparql.html
ARC for PHP, http://arc.semsol.org/
RAP – RDF API for PHP
http://www4.wiwiss.fu-berlin.de/bizer/rdfapi/index.html
SPARQL Wrapper (Python),
http://sparql-wrapper.sourceforge.net/
PySPARQL (Python), http://code.google.com/p/pysparql/
DARQ (Distributed ARQ), http://darq.sourceforge.net/
Semantic Web Client library (SWClLib) for Java,
http://www4.wiwiss.fu-berlin.de/bizer/ng4j/semwebclient/
Listing on this slide by O. Hartig, J. Sequeda
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125. What’ll come next
Part 2: Linked Multimedia
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