Slide 1

Faculty of Mathematics and Physics Charles University in Prague Linked Data Tutorial Tom Knap, Jindich Mynarz, Martin Neask, Jakub Strka February 16, 2012 (Partially based on slides of Chris Bizer [9])

Slide 2

16th February 2012 | Linked Data Tutorial2 Motivation

Slide 3

16th February 2012 | Linked Data Tutorial3 Motivational Scenario Basic data EmployeesDepartments Public contracts BudgetExpenses WWW page of the institution Business Register FIS Buyers Profile ISVZUS gov.cz Data Consumer: Show me suppliers of the public contracts for the Ministry of Finance (MF) in the region Liberec. Show me the data on the Google maps in iPhone. For every public contract, I am also looking for the aggregation of all the payments made by MF, link to their budget and responsible person. Where can I get the data about public contracts, responsible persons, expenses, and budget of MF? How should I aggregate and link the data? How can I observe the data on the map?

Slide 4

16th February 2012 | Linked Data Tutorial4 Current Common Practise 1 MF public contracts 2 MF public contracts + employees 3 - Expenses Consumer did not discovered ? ? ? Information Integration very time consuming, boring, and ineffective! Basic data EmployeesDepartments Public contracts BudgetExpenses WWW page of the institution Business Register FIS Buyers Profile ISVZUS gov.cz

Slide 5

16th February 2012 | Linked Data Tutorial5 Linked Data - Basics

Slide 6

16th February 2012 | Linked Data Tutorial6 Linked Data Set of best practices for publishing structured data on the Web in accordance with the general architecture of the Web using Semantic Web technologies and standards Semantic Web is the goal, Linked Data provides the means to reach the goal

Slide 7

16th February 2012 | Linked Data Tutorial7 Linked Data Principles 1.Use URIs as names for things 2.Use HTTP URIs so that people can look up those names. 3.When someone looks up a URI, provide useful RDF information 4.Include RDF statements that link to other URIs so that they can discover related things. [Tim Berners-Lee, http://www.w3.org/DesignIssues/LinkedData.html, 2006]

Slide 8

16th February 2012 | Linked Data Tutorial8 Architecture of the Classic Web Single global information space Small set of simple standards: HTTP URI globally unique ID retrieval mechanism HTML as document format Hyperlinks to connect everything Applications work on top of the complete information space

Slide 9

16th February 2012 | Linked Data Tutorial9 Web 2.0 APIs and Mashups No single global dataspace Shortcomings: API have proprietary interfaces No hyperlinks between data items within different APIs Mashups are based on a fixed set of data sources Web APIs slice the Web into Walled Gardens!

Slide 10

16th February 2012 | Linked Data Tutorial10 Linked Data Extend the Web with a single global dataspace By using RDF to publish structured data on the Web By setting links between data items within different data sources. Physically distributed, behaves like single dataspace

Slide 11

16th February 2012 | Linked Data Tutorial11 RDF Data Model Flexible graph-based data model [2] HTTP URIs take the role of global primary keys. pd:cygri = http://richard.cyganiak.de/foaf.rdf#cygri dbpedia:Berlin = http://dbpedia.org/resource/Berlin

Slide 12

16th February 2012 | Linked Data Tutorial12 Resolving URIs over the Web The HTTP protocol brings together identification and retrieval

Slide 13

16th February 2012 | Linked Data Tutorial13 Following Links deeper into the Web

Slide 14

16th February 2012 | Linked Data Tutorial14 Pubby Linked Data Browser http://dbpedia.org/page/esk_Krumlov

Slide 15

16th February 2012 | Linked Data Tutorial15 Properties of the Web of Linked Data Global, distributed data space build on a simple set of standards RDF, URIs, HTTP Entities are connected by links creating a global data graph that spans data sources enables the discovery of new data sources Data-coexistence Everyone can publish data to the Web of Linked Data Everyone can express their personal view on things

Slide 16

16th February 2012 | Linked Data Tutorial16 Linked Data Deployment on the Web.. Is it real?

Slide 17

16th February 2012 | Linked Data Tutorial17 W3C Linking Open Data Project Grassroots community effort to Publish existing open license datasets as Linked Data on the Web Interlink things between different data sources

Slide 18

16th February 2012 | Linked Data Tutorial18 Linked Data Cloud 2007

Slide 19

16th February 2012 | Linked Data Tutorial19 Linked Data Cloud 2009

Slide 20

16th February 2012 | Linked Data Tutorial20 Linked Data Cloud 2011 http://richard.cyganiak.de/2007/10/lod/lod-datasets_2011-09-19_colored.pdf http://thedatahub.org/

Slide 21

16th February 2012 | Linked Data Tutorial21 More Statistics http://stats.lod2.eu/stats

Slide 22

16th February 2012 | Linked Data Tutorial22 Uptake in Governmental Domain The EU is publishing LinkedData EuroStat http://estatwrap.ontologycentral.com/http://estatwrap.ontologycentral.com/ National efforts The Government is releasing public data http://data.gov.uk/http://data.gov.uk/ Lots of initiatives in Great Britain Budget in Germany http://bund.offenerhaushalt.de/http://bund.offenerhaushalt.de/ Open Data in Catalonia http://opendata.gencat.cat/en/dades-obertes.htmlhttp://opendata.gencat.cat/en/dades-obertes.html

Slide 23

16th February 2012 | Linked Data Tutorial23 Data.gov.uk http://data.gov.uk/organogram/cabinet-office

Slide 24

16th February 2012 | Linked Data Tutorial24 Linked Data Applications ? ? ? ? Linked Data Browsers

Slide 25

16th February 2012 | Linked Data Tutorial25 Search Engines - Sig.ma http://sig.ma

Slide 26

16th February 2012 | Linked Data Tutorial26 Mashups Public Contracts On the Map http://gd.projekty.ms.mff.cuni.cz:2021/new/map.html

Slide 27

16th February 2012 | Linked Data Tutorial27 Mashups Crime, Transport, Education http://apps.seme4.com/see-uk/

Slide 28

16th February 2012 | Linked Data Tutorial28 Other Applications Browsers: Disco Hyperdata Browser http://www4.wiwiss.fu-berlin.de/rdf_browser/http://www4.wiwiss.fu-berlin.de/rdf_browser/ OpenLink RDF Browser http://ode.openlinksw.com/http://ode.openlinksw.com/ Search Engines Falcons http://ws.nju.edu.cn/falcons/http://ws.nju.edu.cn/falcons/ Watson http://watson.kmi.open.ac.uk/WatsonWUI/ Mashups

Slide 29

16th February 2012 | Linked Data Tutorial29 Linked Data Applications - Summary Linked Data Browsers Search Engines Linked Data Mashups

Slide 30

16th February 2012 | Linked Data Tutorial30 Publishing Linked Data

Slide 31

16th February 2012 | Linked Data Tutorial31 Publishing Tasks Bizer 38 1. Make data available as RDF via HTTP Requires ways to serialize RDF data model 2. Set RDF links pointing at other data sources 3. Make your data self-descriptive

Slide 32

16th February 2012 | Linked Data Tutorial32 RDF/XML W3C Recommendation, 2004 [2]

Slide 33

16th February 2012 | Linked Data Tutorial33 Turtle Syntax @prefix rdf:. @prefix dataModel:. @prefix myContact:. myContact:me rdf:type dataModel:Person ; dataModel:fullName "Eric Miller". dataModel:mailbox. dataModel:personalTitle "Dr.". W3C Team Submission, 2011, [4]

Slide 34

16th February 2012 | Linked Data Tutorial34 RDFa A way to directly add RDF to XHTML pages Provides new attributes to handle additional markup W3C Recommendation, 2008 [5] HTML is not extendable most RDFa parsers will recognize RDFa attributes in any version of HTML

Slide 35

16th February 2012 | Linked Data Tutorial35 RDFa Provides new attributes to handle additional markup, reuses existing About, resource, Href, src, Used with any supported element, prefered: Span, div (in the body) a (linking element) Meta, link (in the header)

Slide 36

16th February 2012 | Linked Data Tutorial36 RDFa Example XHTML page http://example.com/alice/posts/42 Original XHTML code All content on this site is licensed under a Creative Commons License. XHTML + RDFa All content on this site is licensed under a Creative Commons License. RDF triples destilled from XHTML+RDFa cc:license.

Slide 37

16th February 2012 | Linked Data Tutorial37 RDF store + Linked Data Interface Virtuoso + pubby

Slide 38

16th February 2012 | Linked Data Tutorial38 D2R server A way how to publish data in relational databases as Linked Data Requests from the Web are rewritten into SQL queries via the mapping. on-the-fly translation eliminates the need for replicating the data into a dedicated RDF triple store.

Slide 39

16th February 2012 | Linked Data Tutorial39 Publishing Tasks 1. Make data available as RDF via HTTP 2. Set RDF links pointing at other data sources 3. Make your data self-descriptive

Slide 40

16th February 2012 | Linked Data Tutorial40 2. Set RDF links owl:sameAs. There are tools to help you generate links Silk [6]

Slide 41

16th February 2012 | Linked Data Tutorial41 Publishing Tasks 1. Make data available as RDF via HTTP 2. Set RDF links pointing at other data sources 3. Make your data self-descriptive

Slide 42

16th February 2012 | Linked Data Tutorial42 3. Make your data self-descriptive Increase the usefulness of your data and ease data integration Aspects of self-descriptiveness 1. Reuse terms from common vocabularies 2. Enable clients to retrieve the schema 3. Publish schema mappings for proprietary terms 4. Metadata Provide provenance metadata Provide licensing metadata Provide data-set-level metadata using voiD

Slide 43

16th February 2012 | Linked Data Tutorial43 About Vocabularies We have to be able to define the meaning of the subject, properties Vocabularies, e.g. Public contracts ontology

Slide 44

16th February 2012 | Linked Data Tutorial44 Public Contracts Ontology http://purl.org/procurement/public-contracts#

Slide 45

16th February 2012 | Linked Data Tutorial45 RDFS RDFS = RDF Schema W3C recommendation http://www.w3.org/TR/rdf-schema/ Vocabulary for RDF Definition of classes is:Student rdf:type rdfs:Class Definition of properties is:name rdf:type rdfs:Property Domains and ranges of properties is:name rdfs:domain is:Student is:name rdfs:range xsd:string

Slide 46

16th February 2012 | Linked Data Tutorial46 OWL OWL = Web Ontology Language W3C recommendation http://www.w3.org/TR/owl2-overview/ Ontologies More complex constructs Class or property equivalences Cardinality restrictions

Slide 47

16th February 2012 | Linked Data Tutorial47 3. Make your data self-descriptive Increase the usefulness of your data and ease data integration Aspects of self-descriptiveness 1. Reuse terms from common vocabularies 2. Enable clients to retrieve the schema 3. Publish schema mappings for proprietary terms 4. Metadata Provide provenance metadata Provide licensing metadata Provide data-set-level metadata using voiD

Slide 48

16th February 2012 | Linked Data Tutorial48 3.1 Reuse Terms from Common vocabularies Common Vocabularies Friend-of-a-Friend for describing people and their social network SIOC for describing forums and blogs SKOS for representing topic taxonomies Organization Ontology for describing the structure of organizations GoodRelations provides terms for describing products and business entities Music Ontology for describing artists, albums, and performances Review Vocabulary provides terms for representing reviews Common sources of identifiers (URIs) for real world objects LinkedGeoData and Geonames locations GeneID and UniProt life science identifiers DBpedia wide range of things

Slide 49

16th February 2012 | Linked Data Tutorial49 3.2 Enable Clients to retrieve the Schema Clients can resolve the URIs that identify vocabulary terms in order to get their RDFS or OWL definitions. If we discover in data URI: http://purl.org/procurement/public-contracts#awardDate "2011-11-11"^^ ; We resolve the URI and get the definition: RDFS or OWL definition

Slide 50

16th February 2012 | Linked Data Tutorial50 3.3 Publish Schema Mappings pc:Tender a owl:Class ; rdfs:subClassOf gr:Offering. pc:AwardCriterion a owl:Class ; owl:equivalentClass loted:AwardCriteria. Simple Mappings: rdfs:subClassOf, rdfs:subPropertyOf owl:equivalentClass, owl:equivalentProperty Complex mappings R2R [7]

Slide 51

16th February 2012 | Linked Data Tutorial51 3.4 Metadata Licenses Data Provenance Dataset description

Slide 52

16th February 2012 | Linked Data Tutorial52 Consuming Linked Data

Slide 53

16th February 2012 | Linked Data Tutorial53 Overview URI -> Description Pubby Keyword -> Description Sig.ma SPARQL query language [8] SQL for RDF databases

Slide 54

16th February 2012 | Linked Data Tutorial54 SPARQL Example Contracts of the given supplier

Slide 55

16th February 2012 | Linked Data Tutorial55 SPARQL Example - Result

Slide 56

16th February 2012 | Linked Data Tutorial56 Issues of the Simple Consuming Scenarios How to aggregate the data if the links are missing, the data models (ontologies) differs? How to deal with data quality? Everybody can say whatever he wants! Solution: We are developing an infrastructure for cleaning, linking, and aggregating Linked Data Reusing existing technologies, such as Silk

Slide 57

16th February 2012 | Linked Data Tutorial57 ODCleanStore Cleaning the data Custom cleaners Linking the data Silk Graphical user interface Smart data consuming Data aggregation (due to links, ontology mappings) Conflict resolution Data provenance

Slide 58

16th February 2012 | Linked Data Tutorial58 Motivational Scenario - Recall Basic data EmployeesDepartments Public contracts BudgetExpenses WWW page of the institution Business Register FIS Buyers Profile ISVZUS gov.cz Data Consumer: Show me suppliers of the public contracts for the Ministry of Finance (MF) in the region Liberec. Show the data on the Google maps in iPhone. For every public contract, I am looking for the aggregation of all the payments made by MF, link to their budget and responsible person. Where can I get the data about public contracts, responsible persons, expenses, and budget of MF? How should I aggregate and link the data? How can I observer the data on the map?

Slide 59

16th February 2012 | Linked Data Tutorial59 Goal ODCleanStore Basic data EmployeesDepartments Public contracts BudgetExpenses WWW page of the institution Business Register FIS Buyers Profile ISVZUS gov.cz

Slide 60

16th February 2012 | Linked Data Tutorial60 Conclusions

Slide 61

16th February 2012 | Linked Data Tutorial61 Linked Data vs. Open Data Open data 3 stars! 4th star: Single and flexible model (RDF) is missing 5th star: Links Open data are raw data, which are freely available on the Web to: Everyone Anytime For whatever purpose

Slide 62

16th February 2012 | Linked Data Tutorial62 Conclusions and Take Away Message The Power Of Linked Data (5 star data) Web-scale data publishing with web-based discovery mechanisms Distributed annotation make comments about observations, data series, points on the map Easy to reuse Huge potential when connecting to the cloud, linking the data, the benefits are growing as the amount of data published as Linked Data is increasing Integration on data level Easy to extend (new data properties as required, no need to be planned up-front) Easy to merge no name clashes!

Slide 63

16th February 2012 | Linked Data Tutorial63 Future Steps If you managed to get interesting data, try to publish them as Linked Data! We can help you with the whole lifecycle creating, publishing, maintenance of the data Just create RDF data, we will publish it for you Just let us know (send us the data), we can publish it Publish data in the same way, but use global identifiers according to LD principles When the infrastructure (ODCleanStore) is ready, you can just send us the RDF data using web service and we will do all the other stuffs clean, link, and provide aggregated views.

Slide 64

16th February 2012 | Linked Data Tutorial64 Thank You!

Slide 65

16th February 2012 | Linked Data Tutorial65 References Textbook: Tom Heath, Christian Bizer: Linked Data: Evolving the Web into a Global Data Space. http://linkeddatabook.com/ http://linkeddatabook.com/ [2] http://www.w3.org/TR/rdf-primer/http://www.w3.org/TR/rdf-primer/ [3] http://www.w3.org/TR/REC-rdf-syntax/http://www.w3.org/TR/REC-rdf-syntax/ [4] http://www.w3.org/TeamSubmission/turtle/http://www.w3.org/TeamSubmission/turtle/ [5] http://www.w3.org/TR/rdfa-syntax/http://www.w3.org/TR/rdfa-syntax/ [6] http://www4.wiwiss.fu-berlin.de/bizer/silk/http://www4.wiwiss.fu-berlin.de/bizer/silk/ [7] http://www.w3.org/TR/rdf-sparql-query/

Slide 66

16th February 2012 | Linked Data Tutorial66

Slide 67

16th February 2012 | Linked Data Tutorial67 Thank You!

Slide 68

16th February 2012 | Linked Data Tutorial68 Motivational Scenario (to recall) zkladn daje zamstnancioddlen veejn zakzky rozpoetvdaje WWW strnky instituce Obchodn rejstk FIS Profil zadavatele ISVZUS gov.cz Uivatel: Dodavatel veejnch zakzek MF z Libereckho kraje na Google mapch v iPhone aplikaci. Pro kadou zakzku agregace nebo vpis plateb, vazbu na rozpoet a zodpovdnou osobu. Kde zskm data o zakzkch, odpovdnch osobch, vdajch a rozpotu MF? Jak mm data slouit a provzat? Jak zobrazit data v iPhone na map?

Slide 69

16th February 2012 | Linked Data Tutorial69 Searching on the Current Web Searching information about the American city London in Ohio Input: keywords London Result: London (in Britain) Searching is implemented based on which documents contain the given keywords It is up to the user to read and interpret the results

Slide 70

16th February 2012 | Linked Data Tutorial70 Information Integration on the Web Looking for Indian food for the Saturdays night dinner with a girlfriend Step 1: Search restaurants specialized in Indian cuisine, get the address Step 2: Open up new tab, go to the favourite map utility to get the driving directions to the restaurants Step 3: Select the closest one An integration process, you get some information (address), which you use to get more information (directions)

Slide 71

16th February 2012 | Linked Data Tutorial71 Data Mining on the Current Web An application for collecting stock information from the given set of Web sites, reporting every 10 minutes Specialized piece of software Re-code if something important has changed E.g. layout of one single page Re-code if more pages should be added ablona XRG71

Slide 72

16th February 2012 | Linked Data Tutorial72 Problems of the Current Web? Web aimed for human readers, display oriented, web servers/browsers do not understand the content of the page - they just know how to display the page What is necessary: There has to be a way (model) to represent knowledge on the Web, shared among pages There has to be a way to create these statements on each Web site The statements should involve common terms and relations, at least for the given domain, there should be a way to define them Agent should be able to conduct reasoning Agent should be able to query the statements ablona XRG72

Slide 73

16th February 2012 | Linked Data Tutorial73 Semantic Web Is an extension of the current Web in which information is given well-defined meaning, better enabling computers and people to work in cooperation The Semantic Web is a collection of technologies and standards that allow machines to understand the meaning (semantics) of information on the Web ablona XRG73

Slide 74

16th February 2012 | Linked Data Tutorial74 TODO How can Linked Data Help us in the Motivational Scenarios? Searching Specifying that I am looking for a city Than starting writing London, the combo box appears: http://dbpedia.org/resource/Londonhttp://dbpedia.org/resource/London http://dbpedia.org/resource/London_Ontariohttp://dbpedia.org/resource/London_Ontario http://dbpedia.org/resource/London_Ohiohttp://dbpedia.org/resource/London Information Integration Faceted browsing, filter all restaurants based on the type of food, distance from my place, opening hours, Data Mining The application can understand the meaning of the Web pages No re-coding for new pages, no re-coding if the layout changes, generic piece of software

Slide 75

16th February 2012 | Linked Data Tutorial75 1. Publishing Patterns? Bizer 39 Zadas URI dostanes reprezentaci Vrstvy, nen teba vytvaret nova data Reprezentace se da prizpusobit potrebam -> RDF/XML XHTML+RDFa Shows HOW to make data available as RDF via HTTP

Slide 76

16th February 2012 | Linked Data Tutorial76 RDFa A way to directly add RDF to XHTML pages Provides new attributes to handle additional markup W3C Recommendation (2008) HTML is not extendable most RDFa parsers will recognize RDFa attributes in any version of HTML

Slide 77

16th February 2012 | Linked Data Tutorial77 RDFa Provides new attributes to handle additional markup, reuses existing About, resource, Href, src, Used with any supported element, prefered: Span, div (in the body) a (linking element) Meta, link (in the header)

Slide 78

16th February 2012 | Linked Data Tutorial78 Example Default subject XHTML page http://example.com/alice/posts/42 All content on this site is licensed under a Creative Commons License. RDF triple cc:license.

Slide 79

16th February 2012 | Linked Data Tutorial79 Example 2 Attribute Property XHTML page http://example.com/alice/posts/42 The trouble with Bob Alice... The trouble with Bob Alice...

Slide 80

16th February 2012 | Linked Data Tutorial80 Example 3 Adding attribute about XHTML page http://example.com/alice/posts/42 The trouble with Bob Alice......

Slide 81

16th February 2012 | Linked Data Tutorial81 Example 4 Redefining about XHTML page http://example.com/alice/posts/42 The trouble with Bob Bob takes much better photos than I do: Beautiful Sunset by Bob.

Slide 82

16th February 2012 | Linked Data Tutorial82 Example 5 Blank Node XHTML page http://example.com/alice/posts/42 Alice Birpemswick Email: alice@example.com alice@example.com Phone: +1 617.555.7332

Slide 83

16th February 2012 | Linked Data Tutorial83 Example 6 - Chaining Albert Einstein 1879-03-14 Federal Republic of Germany

Slide 84

16th February 2012 | Linked Data Tutorial84 Establishing Context, Completing @about, @src, @typeof @about and @src explicitly create a new context for statements, @typeof does so implicitly If not present, the context is inherited Subject can be the whole document @About, @rel, @resource@rel @resource -> subject of the second triple is deduced @About, @rel, @property @content -> Object and subject of the triples is deduced as blank node

Slide 85

16th February 2012 | Linked Data Tutorial85 Objects Literal can be set by using @property to express a predicate and then using either @content, or the inline text of the element that @property is on. URI resource can be set using one of @rel or @rev to express a predicate, and then either using one of @href, @resource or @src to provide an object resource explicitly, or using the chaining techniques to obtain an object from a nested subject, or from a bnode.

Slide 86

16th February 2012 | Linked Data Tutorial86 Other ways Microformats Fixed vocabulary Uses attribute class Example Jeremy Keith, Clearleft

Slide 87

16th February 2012 | Linked Data Tutorial87 GRDDL W3C Recommendation (2007) To obtain RDF from RDFa XHTML page To obtain RDF from microformats Requires different templates for different microformats

Slide 88

16th February 2012 | Linked Data Tutorial88 Assignment 1 Look at public contract described at http://zakazky.praha.eu/detailZakazky.jsp?zakazkaId=136343 http://zakazky.praha.eu/detailZakazky.jsp?zakazkaId=136343 Download the page Add RDF annotations (in your favorite editor) to specify: Publisher of the document (Jan Novak) Contract title (Nzev) in Czech and English Publication date (Datum vyven) Awarded tender together with winner of the tender (Dodavatel), and his price (Nabdkov cena) Winner should be accompanied with a name and ICO. Price should be accompanied with the currency information Distill RDF from XHTML file http://www.w3.org/2007/08/pyRdfa/ Notes: You will need to look at: Opendata.cz ontology for public contracts Any other ontology referenced

Slide 89

16th February 2012 | Linked Data Tutorial89 Basic Rules Object is literal Use about, property and content attributes Object is resource (identified by URI) Use about, rel and href attributes

Slide 90

16th February 2012 | Linked Data Tutorial90 Checklist Header version="XHTML+RDFa 1.0 Namespaces Meta publisher Detail -