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Linking Open Data Project
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Defining personal interests
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Defining personal interests
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Hello Open World - The Web of Data for the Pragmatic Developer

WWW2009 Tutorial, Madrid 20th April 2009 - http://hellooopenworld.net

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Hello Open World - The Web of Data for the Pragmatic Developer

  1. 1. Digital Enterprise Research Institute www.deri.ie Hello Open World! The Web of Data for the Pragmatic Developer Alexandre Passant & Michael Hausenblas WWW09, Madrid, Spain 2009-04-20 © Copyright 2008 Digital Enterprise Research Institute. All rights reserved.
  2. 2. Outline Digital Enterprise Research Institute www.deri.ie Content   Motivation   What is the Web of Data?   Creating Structured Data   Discovery, Accessing & Querying   Mash-ups & Advanced Topics   2
  3. 3. Speakers introduction Digital Enterprise Research Institute www.deri.ie Alexandre Passant   Postdoctoral researcher, DERI Galway   Social Software and Semantic Web   http://apassant.net   Michael Hausenblas   Postdoctoral researcher, DERI Galway   Large-scale Data/Linked Data and Multimedia   http://sw-app.org   3
  4. 4. What is this tutorial about Digital Enterprise Research Institute www.deri.ie What you will learn   Web of Data principles   Finding and creating structured data   Ontologies and lightweight inference   Storing and querying RDF data with SPARQL   User interfaces and mash-ups for the Web of Data   What you will not   Ontology mapping and alignment   Advanced rules languages   Complex SPARQL querying   4
  5. 5. What you should be able to do after this tutorial Digital Enterprise Research Institute www.deri.ie Explain the Web of Data to your CTO / Students /   Advisor / Grandmother Spread the values of the Web of Data   Publish Linked Data   And participate in the Linking Open Data community effort   to expand the network effort of the Web of Data Build applications for the Web of Data   Using open-source and xAMP technologies   Creating, consuming and mashing-up RDF data   5
  6. 6. Outline Digital Enterprise Research Institute www.deri.ie Content   Motivation   What is the Web of Data?   Creating Structured Data   Discovery, Accessing & Querying   Mash-ups & Advanced Topics   6
  7. 7. Motivation Digital Enterprise Research Institute www.deri.ie 2007 2008 7
  8. 8. Motivation Digital Enterprise Research Institute www.deri.ie 2008 2009 8
  9. 9. Motivation Digital Enterprise Research Institute www.deri.ie More and more data is available on the Web   Structured data, in RDF, microformats, etc.   Up to now people would develop against   proprietary APIs (such as from Flickr, Google, etc.) Loss of time for developers   The Web of Data …   Provides a uniform data model (RDF)   Provides a uniform API for accessing data (RDF/SPARQL)   Provide common semantics for this data (RDFS/OWL)   Is a scalable platform for data integration and mash-up   Enables serendipitous usage of data   9
  10. 10. Outline Digital Enterprise Research Institute www.deri.ie Content   Motivation   What is the Web of Data?   Creating Structured Data   Discovery, Accessing & Querying   Mash-ups & Advanced Topics   10
  11. 11. What is the Web of Data? Digital Enterprise Research Institute www.deri.ie In contrast to the full-fledged Semantic Web vision, the Web of Data is about publishing structured data in RDF using URIs rather than focusing on the ontological level or inference.  This simplification (just as the Web simplified the established academic approaches of Hypertext systems) lowers the entry barrier for data providers and consumers, hence fosters a wide-spread adoption and real-world impact. 11
  12. 12. What is the Web of Data? Digital Enterprise Research Institute www.deri.ie 12
  13. 13. What is the Web of Data? Digital Enterprise Research Institute www.deri.ie Linked data principles, by Tim Berners-Lee, ca.   2006 Use URIs to identify things (anything, not just documents)   Use HTTP URIs – globally unique names, distributed   ownership – allows people to look up things Provide useful information in RDF – when someone looks   up a URI Include RDF links to other URIs – to enable discovery of   related information 13
  14. 14. What is the Web of Data? Digital Enterprise Research Institute www.deri.ie Ongoing work   Description/discovery   –  semantic sitemaps, see http://sw.deri.org/2007/07/sitemapextension/ –  voiD, see http://semanticweb.org/wiki/VoiD Trust (SPOT09 at ESWC09 for example)   Multimedia/Fragments, see   http://www.interlinkingmultimedia.info/ Foundational issues in TAG/AWWSW   Transforming the read-only Web of Data into a read/write   Web of Data, see for example http://esw.w3.org/topic/PushBackDataToLegacySources 14
  15. 15. What is the Web of Data? - URIs Digital Enterprise Research Institute www.deri.ie Architecture of the World Wide Web, vol. 1   http://www.w3.org/TR/webarch/   “To benefit from and increase the value of the World Wide   Web, agents should provide URIs as identifiers for resources” URIs are used to identifying anything that can be   represented on the Web: pages but also people, cities, interests … But people are not documents !   15
  16. 16. What is the Web of Data? - URIs Digital Enterprise Research Institute www.deri.ie A Uniform Resource Identifier (URI) is a compact   sequence of characters that identifies an abstract or physical resource as of RFC3986 Syntax   URI = scheme quot;:quot; hier-part [ quot;?quot; query ] [ quot;#quot; fragment ] Example   foo://example.com:8042/over/there?name=ferret#nose _/ _________________/_________/ __________/ __/ | | | | | scheme authority path query fragment 16
  17. 17. What is the Web of Data? - URIs Digital Enterprise Research Institute www.deri.ie Don’t confuse scheme with protocol   Scheme: defines URI layout and (certain) semantics; go and   register with IANA using RFC4395 Protocol: defines communication means between   endpoints (such as HTTP, FTP, etc.) URI resolution (as of RFC3986)   STEP OUTPUT BUFFER INPUT BUFFER 1: /a/b/c/./../../g 2E: /a /b/c/./../../g 2E: /a/b /c/./../../g 2E: /a/b/c /./../../g 2B: /a/b/c /../../g 2C: /a/b /../g 2C: /a /g 2E: /a/g 17
  18. 18. What is the Web of Data? - URIs Digital Enterprise Research Institute www.deri.ie URIrefs, URI references   An RDF URI reference is a Unicode string does not contain any control characters (#x00 - #x1F, #x7F-#x9F) and would produce a valid URI character sequence representing an absolute URI when subjected to an UTF-8 encoding along with %-escaping non-US-ASCII octets. QNames, Qualified Names (see XML Namespaces)   XML’s way to allow namespaced elements/attributes as of QName = Prefix ‘:‘ LocalPart CURIEs, Compact URIs   Generic, abbreviated syntax for expressing URIs, currently   in SPARQL, RDFa, and XHTML2 deployed 18
  19. 19. What is the Web of Data? - HTTP Digital Enterprise Research Institute www.deri.ie The Hypertext Transfer Protocol (HTTP) is an   application-level protocol for distributed, collaborative, hypermedia information systems. It is a generic, stateless, protocol which can be used for many tasks beyond its use for hypertext, such as name servers and distributed object management systems, through extension of its request methods, error codes and headers. A feature of HTTP is the typing and negotiation of data representation, allowing systems to be built independently of the data being transferred. [RFC2616] 19
  20. 20. What is the Web of Data? - HTTP Digital Enterprise Research Institute www.deri.ie HTTP messages consist of requests from client to   server and responses from server to client Set of methods is predefined (such as GET, POST,   etc.), but can be expanded Set of status codes is defined   Informational 1xx, provisional response, (100 Continue)   Successful 2xx, request successfully received, understood, and   accepted (201 Created) Redirection 3xx, further action needs to be taken by user agent   to fulfill the request (301 Moved Permanently) Client Error 4xx, client erred (405 Method Not Allowed)   Server Error 5xx, server encountered an unexpected condition   (501 Not Implemented) 20
  21. 21. What is the Web of Data? - HTTP Digital Enterprise Research Institute www.deri.ie GET /html/rfc2616 HTTP/1.1 REQUEST Host: tools.ietf.org User-Agent: Mozilla/5.0 Accept: text/html,application/xhtml +xml,application/xml;q=0.9,*/*;q=0.8 RESPONSE HTTP/1.x 200 OK Date: Thu, 05 Mar 2009 08:17:33 GMT Server: Apache/2.2.11 Content-Location: rfc2616.html Last-Modified: Tue, 20 Jan 2009 09:16:04 GMT Content-Type: text/html; charset=UTF-8 21
  22. 22. What is the Web of Data? - HTTP Digital Enterprise Research Institute www.deri.ie Content Negotiation (CN, conneg) is the process of   selecting the best representation for a given response when there are multiple representations available Three types of CN: server-driven, agent-driven CN,   transparent CN Example   curl -I -H quot;Accept: application/rdf+xmlquot; http://dbpedia.org/resource/Galway HTTP/1.1 303 See Other Content-Type: application/rdf+xml Location: http://dbpedia.org/data/Galway.rdf 22
  23. 23. What is the Web of Data? - HTTP Digital Enterprise Research Institute www.deri.ie Caching (see Cache–Control header field) is   essential for scalability HTTPbis, IETF WG chaired by Mark Nottingham,   mainly about: patches, clarifications, deprecate non-used features, documentation of security properties 23
  24. 24. What is the Web of Data? - HTTP Digital Enterprise Research Institute www.deri.ie Representational State Transfer   resource the intended conceptual target of a hypertext reference resource identifier URL, URN representation HTML document, JPEG image representation media type, last-modified time metadata resource source link, alternates, vary metadata control data if-modified-since, cache-control 24
  25. 25. What is the Web of Data? - RDF Digital Enterprise Research Institute www.deri.ie As of RDF abstract syntax, a data model: a directed,   labeled graph based on URIs RDF is not XML !   RDF/XML is only one of the multiple way to serialize RDF   data (N3, RDFa …) Triple: (subject predicate object)   subject … URIref or bNode   predicate … URIref   object … URIref or bNode or literal   <http://sw-app.org/#i> <http://xmlns.com/foaf/0.1/knows> <http://apassant.net/alex>. 25
  26. 26. What is the Web of Data? - RDF Digital Enterprise Research Institute www.deri.ie 26
  27. 27. What is the Web of Data? - Ontologies Digital Enterprise Research Institute www.deri.ie Ontologies provide common semantics for the Web   of Data “An ontology is a specification of a conceptualization.”   Main languages are RDFS and OWL   This tutorial will mainly focus on RDFS   OWL allows advanced axioms (contraints, unions …)   Classes and properties   :Person a rdfs:Class   :father a rdfs:Property   :father rdfs:domain :Person   :father rdfs:range :Person   27 of XYZ
  28. 28. What is the Web of Data? - Ontologies Digital Enterprise Research Institute www.deri.ie Hierarchies in ontologies   Are needed to define narrower / broader concepts   :LivingThing > :Person   Can be applied to both classes and properties   :Person rdfs:subClassOf :LivingThing   :father rdfs:subPropertyOf :familyRelation   Inference engines can take advantage of it to create   new facts Can be used when querying information   Retrieve all :LivingThing instances with a :familyRelation   –  Will get :Person and :father 28 of XYZ
  29. 29. What is the Web of Data? – Open World Digital Enterprise Research Institute www.deri.ie The Open World Assumption   Might be complex to understand when coming from a   RDBMS or OOP background If a fact is not there, it does not means it is false   Bob’s father is Paul. Is Jim Paul’s father ?   –  Cannot be answered unless there are some cardinality constraints in the ontology (in OWL), e.g. a Person has only 1 father. Is John a speaker in this tutorial ?   –  Cannot be answered Bob’s daughters are Alice and June. Has Bob 3 daughters ?   –  Cannot be answered 29 of XYZ
  30. 30. What is the Web of Data? – Open World Digital Enterprise Research Institute www.deri.ie Domain and range of properties are descriptive, not   prescriptive :father rdfs:domain :Person   Does not mean that only pre-defined instances of :Person   can be linked to other via a :father relationship, but that each instance linked to another via :father becomes instantaneously a foaf:Person –  Based on RDF semantics (Rule rdfs2) –  http://www.w3.org/TR/rdf-mt/ Once again, constraints are needed to check integrity of a   model and a knowledge base –  E.g. to check that inferred statements are not contradictory with OWL axioms such as owl:disjoinwWith 30 of XYZ
  31. 31. What is the Web of Data? - Overview Digital Enterprise Research Institute www.deri.ie Web's Standard Retrieval Algorithm as of [SDD]: 1.  parse URI and find HTTP protocol 2.  look up DNS name to determine the associated IP address 3.  open a TCP stream to port 80 at the IP address determined above 4.  format an HTTP GET request for resource and sends that to the server 5.  read response from the server 6.  from the status code (200) determine that a representation of the resource is available 7.  inspect the returned Content-Type 8.  pass the entity-body to its HTML rendering engine 31
  32. 32. Digital Enterprise Research Institute www.deri.ie 32
  33. 33. What is the Web of Data? - Overview Digital Enterprise Research Institute www.deri.ie 33
  34. 34. What is the Web of Data? - Overview Digital Enterprise Research Institute www.deri.ie 34
  35. 35. Applications for the Web of Data Digital Enterprise Research Institute www.deri.ie Towards a reference architecture for Semantic Web applications. Heitmann et al. (WebSci09 – http://journal.webscience.org/199/) 35 of XYZ
  36. 36. Linking Open Data Project Digital Enterprise Research Institute www.deri.ie Community project with W3C support started in   early 2007 [LOD] Idea: take existing (open) data sets and make   them available on the Web in RDF Interlink them with other data sets   Kudos to Tom Heath and Richard Cyganiak; the material in this section is heavily based on their work. 36
  37. 37. Linking Open Data Project Digital Enterprise Research Institute www.deri.ie May 2007 37
  38. 38. Linking Open Data Project Digital Enterprise Research Institute www.deri.ie Feb 2009 38
  39. 39. Linking Open Data Project Digital Enterprise Research Institute www.deri.ie DBpedia 39
  40. 40. Linking Open Data Project Digital Enterprise Research Institute www.deri.ie Geonames 40
  41. 41. Tools and Applications Digital Enterprise Research Institute www.deri.ie Linking Open Data homepage [LOD] has   Browsing with Tabulator, VisiNav, DBpedia Mobile, iLOD,   etc. Searching with Sindice, SWSE, Falcons, etc.   Mashups, e.g. Revyu, BBC Music, DERI Pipes   See further   http://esw.w3.org/topic/SweoIG/TaskForces/ CommunityProjects/LinkingOpenData/Applications 41
  42. 42. Tools and Applications Digital Enterprise Research Institute www.deri.ie DBpedia Mobile 42
  43. 43. Tools and Applications Digital Enterprise Research Institute www.deri.ie BBC music beta 43
  44. 44. Outline Digital Enterprise Research Institute www.deri.ie Content   Motivation   What is the Web of Data?   Creating Structured Data   Discovery, Accessing & Querying   Mash-ups & Advanced Topics   44 of XYZ
  45. 45. Creating Structured Data Digital Enterprise Research Institute www.deri.ie Overview of different methods:   Create RDF/XML manually (using your favourite text-editor   or Web-based interfaces) Create XHTML+RDFa documents and use GRDDL   transformation Use exporters / wrappers for existing service   Use applications that natively expose RDF data   Provide mappings from RDBMS to RDF data   Hands-on !   We will go through several of them to create interlinked   RDF data from various sources of structured data 45 of XYZ
  46. 46. Getting a FOAF profile Digital Enterprise Research Institute www.deri.ie Or how to give yourself a URI   FOAF is the main vocabulary to describe people,   their interests, their social networks http://foaf-project.org   http://xmlns.com/foaf/0.1   Create your FOAF file   http://www.ldodds.com/foaf/foaf-a-matic (requires   hosting - provided during the tutorial) http://foafbuilder.qdos.com/builder/ (requires OpenID)   46 of XYZ
  47. 47. Extend your FOAF profile Digital Enterprise Research Institute www.deri.ie The foaf:knows property aims to represent social   connections between people :alex foaf:knows :michael   Going further with the relationship vocabulary   http://vocab.org/relationship/: colleagueOf, hasMet …   Add some people from the workshop, validate, and   upload to the workshop repository http://www.w3.org/RDF/Validator/   http://helloopenworld.net/www2009/data   You finally got a URI !   –  http://helloopenworld.net/www2009/data/apassant.rdf#me 47 of XYZ
  48. 48. Defining personal interests Digital Enterprise Research Institute www.deri.ie Instead of modeling interests as plain-text strings,   use URIs to describe them ! Allows interlinking of various resources for advanced   query purposes: “find all people that like movies directed by Tarantino” And link them to you using foaf:topic_interest   :me foaf:topic_interest :movie   But … where to get these URIs ?   The Linking Open Data cloud !   –  Provide URIs for million of concepts, esp. thanks to DBpedia Sindice can be used to find URIs for a given concept   –  http://sindice.com 48 of XYZ
  49. 49. Defining personal interests Digital Enterprise Research Institute www.deri.ie 49 of XYZ
  50. 50. Defining personal interests Digital Enterprise Research Institute www.deri.ie 50 of XYZ
  51. 51. Extending a vocabulary Digital Enterprise Research Institute www.deri.ie The semantics of foaf:topic_interest can be too   weak How to explicitly create a relationship between someone   and his favorite(s) movie(s) and not any kind of interest ? Extending FOAF by creating your own property   And declare it as a subproperty of foaf:topic_interest   Vocabularies hosting with OpenVocab   Collaborative ontology editing   http://open.vocab.org   http://open.vocab.org/forms/newprop   51 of XYZ
  52. 52. RDFa and GRDDL Digital Enterprise Research Institute www.deri.ie GRDDL is a mechanism to transform any kind of   XML to RDF XHTML+RDFa is an XML application, hence GRDDL   can be used to glean the RDF graph from it INRIA/Fabien Gandon provided such an   transformation based on XSLT, now available at http://www.w3.org/2008/07/rdfa-xslt 52 of XYZ
  53. 53. RDFa and GRDDL Digital Enterprise Research Institute www.deri.ie The GRDDL Primer at   http://www.w3.org/TR/grddl-primer/#scheduling shows the overall processing of XHTML+RDFa: 53 of XYZ
  54. 54. RDFa and GRDDL Digital Enterprise Research Institute www.deri.ie http://sdow2009.semanticweb.org   54 of XYZ
  55. 55. RDFa and GRDDL Digital Enterprise Research Institute www.deri.ie http://sdow2009.semanticweb.org   Browse source to check RDFa annotations   55 of XYZ
  56. 56. RDFa and GRDDL Digital Enterprise Research Institute www.deri.ie http://sdow2009.semanticweb.org   Header contains prefixes and links to the GRDDL   transformation 56 of XYZ
  57. 57. RDFa and GRDDL Digital Enterprise Research Institute www.deri.ie http://sdow2009.semanticweb.org   Webpage can be translated to native RDF/XML using an   RDFa distiller - http://www.w3.org/2007/08/pyRdfa/ 57 of XYZ
  58. 58. Wrappers for existing sources Digital Enterprise Research Institute www.deri.ie Creating and maintaining a FOAF file by hand can   be a time-consuming task How can we automatically get RDF data from existing   sources ? What about Web 2.0 services in which we already   give lots of personal information ? Most of them provide APIs to get structured information   (JSON, XML …) about the user profiles, content, etc. API to RDF wrappers can easily be implemented   58 of XYZ
  59. 59. Wrappers for Web 2.0 services Digital Enterprise Research Institute www.deri.ie Facebook wrapper   Generates a FOAF file from your Facebook profile   http://www.dcs.shef.ac.uk/~mrowe/foafgenerator.html   Flickr wrapper   Generates FOAF + SIOC + links to geographical information   (using geonames.org) http://apassant.net/home/2007/12/flickrdf   OpenLink URIBurner   Translates many structured sources into RDF   E.g. Twitter:   –  http://linkeddata.uriburner.com/about/rdf/http:// twitter.com/terraces 59 of XYZ
  60. 60. Interlinking identities Digital Enterprise Research Institute www.deri.ie The previous exporters create different URIs   A need to unify your online identity on the Web of Data   owl:sameAs and rdfs:seeAlso   http://www4.wiwiss.fu-berlin.de/bizer/pub/   LinkedDataTutorial/ owl:sameAs: Used to identify two resources with different   URIs as being the same resource   rdfs:seeAlso: “More information about this resource can be found here” owl:InverseFunctionalProperty   foaf:mbox, foaf:openid, etc. can be used to identify   uniqueness for a foaf:Person 60 of XYZ
  61. 61. Interlinking identities and networks Digital Enterprise Research Institute www.deri.ie 61 of XYZ
  62. 62. Native export of RDF data Digital Enterprise Research Institute www.deri.ie CMS can expose RDF data natively using dedicated   plug-ins SIOC Export for Drupal: http://drupal.org/project/SIOC   Provide RDF export of each blog post   –  http://apassant.net/blog/2009/03/07/call-suggested- features-sparql-working-group –  http://apassant.net/sioc/node/235 Using RDF autodiscovery feature in the HTML header   –  So that RDF can be discovered when browsing HTML –  Semantic Radar: http://sioc-project.org/firefox RDFa to be included in Drupal7 code !   –  http://groups.drupal.org/node/16597 –  100.000’s of RDFa-powered websites 62 of XYZ
  63. 63. Overview: SIOC for vBulletin Digital Enterprise Research Institute www.deri.ie 63 of XYZ
  64. 64. Translation services Digital Enterprise Research Institute www.deri.ie What about data already structured but not in RDF ?   JSON, RSS2.0, bibtex, etc …   Translation services can be used   Triplr:   –  http://triplr.org Babel   –  http://simile.mit.edu/babel/ Bibtex (from Bibsonomy) to RDF   http://www.bibsonomy.org/bibtex/   286dc964427792faedb4df90056a6fe98/sirakov http://simile.mit.edu/babel/translator?   reader=bibtex&writer=rdf-xml&mimetype=default 64 of XYZ
  65. 65. Relational to RDF Mapping Digital Enterprise Research Institute www.deri.ie Relational data (RDB) is structured data and can be   mapped to RDF straight-forward Main issues:   Closed-world vs. open-world modeling   Assigning URIs for entities (records)   Mapping language expressivity   For a state-of-the-art see   http://www.w3.org/2005/Incubator/rdb2rdf/ RDB2RDF_SurveyReport.pdf 65 of XYZ
  66. 66. Relational to RDF Mapping Digital Enterprise Research Institute www.deri.ie Standardization   W3C RDB2RDF Incubator Group 2008/2009   Upcoming W3C RDB2RDF Working Group   Current solutions (see state-of-the-art)   D2RQ   –  http://www4.wiwiss.fu-berlin.de/bizer/d2rq/ –  DBLP in RDF: http://dblp.l3s.de/d2r/ OpenLink’s Virtuoso   –  http://www.openlinksw.com/virtuoso/ Triplify   –  http://triplify.org 66 of XYZ
  67. 67. Outline Digital Enterprise Research Institute www.deri.ie Content   Motivation   What is the Web of Data?   Creating Structured Data   Discovery, Accessing & Querying   Mash-ups & Advanced Topics   67 of XYZ
  68. 68. Discovery, Accessing & Querying Digital Enterprise Research Institute www.deri.ie Discovery is the process of starting with a URI and   learn more about the resources that can be accessed or described through it In order to access and query data on the Web, one   needs to know WHERE and HOW WHERE: indexer, search engines, pings   HOW: FYN, sitemaps, voiD (next slide)   68 of XYZ
  69. 69. Discovering RDF data Digital Enterprise Research Institute www.deri.ie Simple case: Follow-Your-Nose by dereferencing   URIs (and hence stepwise browsing the RDF graph) Indexer or crawler may utilize the semantic   sitemaps extension http://sw.deri.org/2007/07/sitemapextension/ Applications using linked data should use voiD, the   vocabulary of interlinked datasets http://semanticweb.org/wiki/VoiD Allows to learn what a dataset is about   Provides quantitative data on interlinking (statistics)   Enables to deliver licensing, provenance and access   information 69 of XYZ
  70. 70. Discovering RDF data Digital Enterprise Research Institute www.deri.ie Ping The Semantic Web   http://pingthesemanticweb.com   A repository of RDF data, provides XML feeds of   newly created information Can be used to build your application without   having to crawl the Web for relevant data A food-chain for applications on the Web of Data   –  http://sunsite.informatik.rwth-aachen.de/Publications/CEUR- WS//Vol-248/paper11.pdf E.g. doap:store   –  http://doapstore.org 70 of XYZ
  71. 71. PTSW food-chain Digital Enterprise Research Institute www.deri.ie 71 of XYZ
  72. 72. Storing and querying RDF data Digital Enterprise Research Institute www.deri.ie Distributed querying   Important to keep intact the decentralized architecture of   the WWW Still experimental, can be quite slow   voiD can be used to identify relevant sources to be queried   Storing data locally and querying   Better performances in terms of querying   But need to deal with data replication   PTSW can be used to find which data to store   72 of XYZ
  73. 73. Setup a SPARQL endpoint Digital Enterprise Research Institute www.deri.ie Lots of triple-store available on the market   Virtuoso, Sesame, Joseki …   Based on various back-ups (MySQL, dedicated FS …)   We will focus on xAMP solutions with ARC2   Lightweight RDF framework for PHP   http://arc.semsol.org   RDF Store based on MySQL   Only a few lines of code to set-up a repository   –  http://helloopenworld.net/www2009/store1/index.phps Using SPARQL+ to LOAD / UPDATE / DELETE RDF data   –  SPARQL being read-only 73 of XYZ
  74. 74. Loading RDF data Digital Enterprise Research Institute www.deri.ie SPARQL is a read-only language   SPARUL and SPARQL+ allow to add / modify / delete   RDF data LOAD <URI> [INTO <URI>]   Will load the RDF data from <URI> into the store before   going into SPARQL querying LOAD your FOAF files in the RDF store   http://helloopenworld.net/www2009/store1/   E.g. LOAD <http://helloopenworld.net/www2009/data/   apassant.rdf> –  NB: To be done in POST mode 74 of XYZ
  75. 75. SPARQL Digital Enterprise Research Institute www.deri.ie SPARQL Protocol and RDF Query Language   “The SQL of the Semantic Web”   Both a protocol and a query language   –  RDF data can be queried via REST Four different query forms   SELECT, CONSTRUCT, ASK, DESCRIBE   We will mainly focus on the first one   SPARQL is based on a graph-matching approach   Retrieve statements that match some patterns in one (or   more) RDF graph(s) 75 of XYZ
  76. 76. SPARQL SELECT Digital Enterprise Research Institute www.deri.ie SELECT all people and their name   http://helloopenworld.net/www2009/files/select1.sparql   PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?person ?name WHERE { ?person a foaf:Person ; foaf:name ?name . } 76 of XYZ
  77. 77. SPARQL CONSTRUCT Digital Enterprise Research Institute www.deri.ie Contruct an RDF graph from other ones   Can be seen as the XSLT of the Semantic Web   http://helloopenworld.net/www2009/files/   construct1.sparql PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX www2009: <http://ex.org/www2009/> CONSTRUCT { ?person a www2009:attendee .} WHERE { ?person a foaf:Person . } 77 of XYZ
  78. 78. SPARQL DESCRIBE Digital Enterprise Research Institute www.deri.ie Get information about a given resource   DESCRIBE is implementation specific   http://helloopenworld.net/www2009/files/desc1.sparql   DESCRIBE < http://helloopenworld.net/www2009/data/ apassant.rdf#me> 78 of XYZ
  79. 79. SPARQL ASK Digital Enterprise Research Institute www.deri.ie Check if a particular pattern matches the RDF graph   Is Alex a foaf:Person ?     http://helloopenworld.net/www2009/files/ask1.sparql PREFIX foaf: http://xmlns.com/foaf/0.1/ ASK { <http://helloopenworld.net/www2009/data/ apassant.rdf#me> a foaf:Person . } 79 of XYZ
  80. 80. SPARQL Protocol Digital Enterprise Research Institute www.deri.ie REST-compliant protocol for SPARQL queries   http://helloopenworld.net/www2009/store1/?   query=PREFIX+foaf%3A+%3Chttp%3A%2F%2Fxmlns.com %2Ffoaf%2F0.1%2F%3E%0D%0ASELECT+%3Fperson+ %3Fname%0D%0AWHERE+{%0D%0A+%3Fperson+a+foaf %3APerson+%3B%0D%0A+++foaf%3Aname+%3Fname+.%0D %0A}%0D%0A&output=htmltab Easy for remote SPARQL querying   SPARCool   Easy SPARQL querying via simple URLs   http://sparcool.net   80 of XYZ
  81. 81. Lightweight inference Digital Enterprise Research Institute www.deri.ie ARC2 does not provide RDFS inference engine   But triggers can be used to write one   http://apassant.net/blog/2008/10/01/lightweight-   subpropertyof-subclassof-inference-arc2 Rule rdfs9: inference on subproperties   http://www.w3.org/TR/rdf-mt/#RDFSRules   Can be done with SPARQL CONSTRUCT and ARC2 triggers   http://helloopenworld.net/www2009/store2/index.phps   http://helloopenworld.net/www2009/files/   ARC2_SubPropertyInferenceTrigger.phps 81 of XYZ
  82. 82. Lightweight inference Digital Enterprise Research Institute www.deri.ie LOAD your profile in the inference-enabled store   http://helloopenworld.net/www2009/store2   Try the following query in both stores   Only the second one deals with subProperty inference   http://helloopenworld.net/www2009/files/select2.sparql   PREFIX foaf: <http://xmlns.com/foaf/0.1/> SELECT ?person WHERE { <YOUR_URI> foaf:knows ?person . } 82 of XYZ
  83. 83. Complex triggers Digital Enterprise Research Institute www.deri.ie LOAD the RDF file corresponding to each user   interest Must be done to avoid issues of distributed SPARQL   querying Trigger designed using SPARQL SELECT + SPARUL   LOAD For each loaded file, check if there are any   foaf:topic_interest and load them into the store http://helloopenworld.net/www2009/files/   ARC2_InterestLoadTrigger.phps http://helloopenworld.net/www2009/store3   83 of XYZ
  84. 84. SPARQL SELECT w/ Triggers Digital Enterprise Research Institute www.deri.ie Advanced querying capabilities   http://helloopenworld.net/www2009/files/select3.sparql   PREFIX foaf: <http://xmlns.com/foaf/0.1/> PREFIX dbo: <http://dbpedia.org/ontology/> SELECT ?person WHERE { ?person foaf:topic_interest [ dbo:director <http://dbpedia.org/resource/ Quentin_Tarantino> . ] } 84 of XYZ
  85. 85. Outline Digital Enterprise Research Institute www.deri.ie Content   Motivation   What is the Web of Data?   Creating Structured Data   Discovery, Accessing & Querying   Mash-ups & Advanced Topics   85 of XYZ
  86. 86. Mash-ups & Advanced Topics Digital Enterprise Research Institute www.deri.ie Applying and extending what we have learned   Displaying and rendering the Web of Data   End-user Interaction, UI   Read/write Web of Data   86 of XYZ
  87. 87. Exhibit faceted browsing Digital Enterprise Research Institute www.deri.ie Exhibit   JavaScript library for faceted browsing   http://www.simile-widgets.org/exhibit/   Can be used directly on the top of a SPARQL   endpoint Thanks to SPARQL CONSTRUCT and the Babel translation   service http://helloopenworld.net/www2009/files/   construct2.sparql http://helloopenworld.net/www2009/exhibit   http://microplanet.sioc-project.org/   –  With geolocation services 87 of XYZ
  88. 88. Ubiquity command Digital Enterprise Research Institute www.deri.ie Ubiquity   Mozilla Firefox command line for the Web   http://ubiquity.mozilla.com/   Find people that like a given topic when browsing   Wikipedia (1) Query Dbpedia to find the related URI   (2) Query the RDF Store to identify related people   Total: 2 SPARQL queries !   http://helloopenworld.net/www2009/ubiquity   http://en.wikipedia.org/wiki/Reservoir_Dogs   88 of XYZ
  89. 89. Ubiquity command Digital Enterprise Research Institute www.deri.ie 89 of XYZ
  90. 90. Mash-ups & Advanced Topics Digital Enterprise Research Institute www.deri.ie Enabling the read/write Web of Data with   pushback/RDForms http://esw.w3.org/topic/ PushBackDataToLegacySources Using linked data, SPARQL CONSTRUCT for   mapping and a fixed-schema vocabulary called RDForms http://rdfs.org/ns/rdforms 90 of XYZ
  91. 91. Mash-ups & Advanced Topics Digital Enterprise Research Institute www.deri.ie 91 of XYZ
  92. 92. Mash-ups & Advanced Topics Digital Enterprise Research Institute www.deri.ie View demos at   http://ld2sd.deri.org/pushback/ Check out code at   http://code.google.com/p/pushback/ Join and contribute!   92 of XYZ
  93. 93. Outline Digital Enterprise Research Institute www.deri.ie Content   Motivation   What is the Web of Data?   Creating Structured Data   Discovery, Accessing & Querying   Mash-ups & Advanced Topics   93 of XYZ
  94. 94. Conclusion Digital Enterprise Research Institute www.deri.ie Web of Data is a reality   Tons of tools and technologies exist to   Create and describe data on the Web   Store and access data on the Web   Discover and query data on the Web   Challenges   Technical issues such as scalability and usability   Social issues (trust, privacy, etc.)   Economic issues (building a critical mass)   –  For example Obama administration using SIOC and linked data is fairly motivating 94 of XYZ
  95. 95. Events Digital Enterprise Research Institute www.deri.ie LDOW2009   http://events.linkeddata.org/ldow2009/   Today, will continue this afternoon   Gathering tonight with the LOD community !   ESWC and ISWC   Major venues for research on the Semantic Web   Triplification challenge   http://triplify.org/Challenge/2009   Deadline 30 May   95 of XYZ
  96. 96. Feedback Digital Enterprise Research Institute www.deri.ie Did you learn something during the tutorial ?   Do you think you can now explain the Web of Data   and build applications ? Which topics that you expected were not covered ?   Feel free to discuss or contact us   alexandre.passant@deri.org   michael.hausenblas@deri.org   #swig on irc.freenode.net   96 of XYZ

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