rdf(s) and sparql

LD4SC Summer School 7th -‐ 12th June, Cercedilla, Spain


1st Summer School on Smart Ci2es and Linked Open Data (LD4SC-‐15)

RDF(S) and SPARQL

Pieter Pauwels, Ghent University


The cool and awesome intro movies

hIps://vimeo.com/36752317 hIps://www.youtube.com/watch?v=4x_xzT5eF5Q 2


Index

•  RDF graphs: the simple basis •  Syntax: talking the talk

–  URIs –  RDF Statements –  Literals –  CollecYons and containers

•  Linked (Open) Data Cloud •  Adding basic structure : RDFS •  Querying: SPARQL

–  The basis –  The SPARQL endpoint –  Some more complex examples

•  Concluding Overview

3


RDF graphs, what are they

RDF graphs are DIRECTED, LABELLED GRAPHS

4

P. Pauwels, D. Van Deursen, R. Verstraeten, J. De Roo, R. De Meyer, R. Van de Walle, J. Van Campenhout. A semantic rule checking environment for building performance checking. Automation in Construction 20(5) 2011, 506-518.

LABELLED

DIRECTED

Triple


RDF graphs, what are they NOT

Hierarchies (cfr. XML) RelaYonal databases (cfr. MySQL, SQLServer)

5

RDF graphs are DIRECTED, LABELLED GRAPHS


A triple

6

Triple

SUBJECT OBJECT PREDICATE


ConnecYng Triples

7

SUBJECT OBJECT PREDICATE

OBJECT

PREDICATE

OBJECT

PREDICATE

OBJECT PREDICATE


The result: an RDF graph

8

LABELLED

DIRECTED

Triple

That is it: simple directed labelled graphs, always remember


Index






9


Talking the RDF language

•  RDF stands for Resource DescripYon Framework •  RDF is a standard data model for describing web resources

–  Note: ‘web resources’ can make statements about anything in the real world: DBPedia, geography, building informaYon, sensors, … anything goes

•  RDF is designed to be read and understood by computers •  RDF is not designed for being displayed to people •  RDF is wriIen in XML •  RDF is a W3C RecommendaYon

10

hIp://www.w3schools.com/webservices/ws_rdf_intro.asp

easily used

usually

-‐> standardisaYon

not a file format, not a syntax, not a schema, … => a data model


The SemanYc Web stack

11

Tim Berners-Lee. WWW past & future, 2003. http://www.w3.org/2003/Talks/0922-rsoc-tbl/.


Syntaxes for serialisaYon

12

Triple

RDF/XML

Turtle (TTL)

NotaYon-‐3 (N3)

…


Expressiveness of syntaxes

13

http://www.w3.org/DesignIssues/diagrams/n3/venn

We s2ck to Turtle today


Example TTL file

@prefix b: <hIp://www.R4SC.net/building#> . @prefix c: <hIp://www.R4SC.net/city#> . <hIp://www.R4SC.net/today#building_1>

b:hasRoom <hIp://www.R4SC.net/today#room_1> ; b:hasName “Our summer school building"; c:partOfCity <hIp://ciYes.com/#cercedilla> .

<hIp://ciYes.com/#cercedilla>

c:closeToCity <hIp://ciYes.com/#madrid> ; c:hasName “Cercedilla” .

14


Example TTL graph


The same thing in RDF/XML

<?xml version="1.0" encoding="UTF-‐8"?> <rdf:RDF xmlns:b="hIp://www.R4SC.net/building#" xmlns:c="hIp://www.R4SC.net/city#" xmlns:rdf="hIp://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#"> <rdf:DescripYon rdf:about="hIp://www.R4SC.net/today#building_1"> <c:partOfCity rdf:resource="hIp://ciYes.com/#cercedilla"/> <b:hasName>Our summer school building</b:hasName> <b:hasRoom rdf:resource="hIp://www.R4SC.net/today#room_1"/> </rdf:DescripYon> <rdf:DescripYon rdf:about="hIp://ciYes.com/#cercedilla"> <c:hasName>Cercedilla</c:hasName> <c:closeToCity rdf:resource="hIp://ciYes.com/#madrid"/> </rdf:DescripYon> </rdf:RDF>

16


Convert to different syntaxes

Convert to/from syntaxes:

hIp://rdf-‐translator.appspot.com/ Or simply build and use your own sosware tool

17


Index






18


Uniform Resource IdenYfiers

URI

URI

URI

URI

URI

URI URI

URI

URI

URI

URI


What is a URI?

•  URI stands for Uniform Resource IdenYfier •  Purpose: Obtain globally unique idenYfiers, so that informaYon

can be exchanged globally. •  Structure:

<hIp://www.R4SC.net/today#building_1>

•  Namespace needed to avoid name conflicts with tags of the same name: other tags with the name “building_1” can be defined with other namespace URIs, and an RDF reader would sYll be able to tell that they were different properYes even though they had the same tag name.

20

Namespace Name


Full version of the URIs

<hIp://www.R4SC.net/today#building_1> <hIp://www.R4SC.net/today#room_1> <hIp://www.R4SC.net/building#hasRoom > <hIp://www.R4SC.net/building#hasName > <hIp://www.R4SC.net/city#partOfCity> <hIp://www.R4SC.net/city#closeToCity> <hIp://www.R4SC.net/city#hasName> <hIp://ciYes.com/#cercedilla> <hIp://ciYes.com/#madrid> 21


Example TTL file





22


Prefixed URIs @prefix b: <hIp://www.R4SC.net/building#> . @prefix c: <hIp://www.R4SC.net/city#> . @prefix bi: <hIp://www.R4SC.net/today#> . @prefix ci: < hIp://ciYes.com/# > . bi:building_1 bi:room_1 b:hasRoom b:hasName c:partOfCity c:closeToCity c:hasName ci:madrid ci:cercedilla

23


TTL file with fully qualified names


<hIp://www.R4SC.net/building#hasRoom > <hIp://www.R4SC.net/

today#room_1> ; <hIp://www.R4SC.net/building#hasName > “Our summer school building"; <hIp://www.R4SC.net/city#partOfCity > <hIp://ciYes.com/#cercedilla> .


<hIp://www.R4SC.net/city#closeToCity > <hIp://ciYes.com/#madrid> ; <hIp://www.R4SC.net/city#hasName > “Cercedilla” .

24

-‐> prefixes increase readibility


Index






25


Statements

Statement

Statement

Statement

Statement

Statement


Statement follows triple structure


<hIp://www.R4SC.net/city#partOfCity > <hIp://ciYes.com/#cercedilla> .

27

Triple

<hIp://www.R4SC.net/

today#building_1>


<hIp://www.R4SC.net/city#partOfCity>


Combining statements


<hIp://www.R4SC.net/building#hasRoom > <hIp://www.R4SC.net/

today#room_1> ; <hIp://www.R4SC.net/building#hasName > “Our summer school building"; <hIp://www.R4SC.net/city#partOfCity > <hIp://ciYes.com/#cercedilla> .


<hIp://www.R4SC.net/city#closeToCity > <hIp://ciYes.com/#madrid> ; <hIp://www.R4SC.net/city#hasName > “Cercedilla” .

28

Same subject

AND [next statement]

Same subject

Same subject AND [next statement]

, ! Same subject, same predicate


List of all statements <hIp://www.R4SC.net/today#building_1> <hIp://www.R4SC.net/building#hasRoom >

<hIp://www.R4SC.net/today#room_1> . <hIp://www.R4SC.net/today#building_1> <hIp://www.R4SC.net/building#hasName > “Our summer school building” . <hIp://www.R4SC.net/today#building_1>

<hIp://www.R4SC.net/city#partOfCity > <hIp://ciYes.com/#cercedilla> . <hIp://ciYes.com/#cercedilla>

<hIp://www.R4SC.net/city#closeToCity > <hIp://ciYes.com/#madrid> . <hIp://ciYes.com/#cercedilla>

<hIp://www.R4SC.net/city#hasName > “Cercedilla” .

29


Statements

Statement

Statement

Statement

Statement

Statement


Index






31


Recap on the URIs

URI

URI

URI

URI

URI

URI URI

URI

URI

URI

URI


Literals in the statements <hIp://www.R4SC.net/today#building_1> <hIp://www.R4SC.net/building#hasRoom >

<hIp://www.R4SC.net/today#room_1> . <hIp://www.R4SC.net/today#building_1> <hIp://www.R4SC.net/building#hasName > “Our summer school building” . <hIp://www.R4SC.net/today#building_1>

<hIp://www.R4SC.net/city#partOfCity > <hIp://ciYes.com/#cercedilla> . <hIp://ciYes.com/#cercedilla>

<hIp://www.R4SC.net/city#closeToCity > <hIp://ciYes.com/#madrid> . <hIp://ciYes.com/#cercedilla>

<hIp://www.R4SC.net/city#hasName > “Cercedilla” .

33

Literal

Literal


ConvenYonal representaYon / disYncYon from regular resources

Resource

Resource

Resource

Resource

Literal

Literal


Similar yet disYnct

@prefix b: <hIp://www.R4SC.net/building#> . @prefix c: <hIp://www.R4SC.net/city#> . @prefix xsd: <hIp://www.w3.org/2001/XMLSchema>. <hIp://www.R4SC.net/today#building_1>

b:hasName “Our summer school building” , “Our summer school building”@en , “Our summer school

building”^^xsd:string

35

Untyped

Typed

Literal with language seWng Referring to type

within specific namespace


What is available in xsd

36

http://www.w3.org/TR/xmlschema-2/


What is available in xsd

37

http://www.xml.dvint.com/docs/SchemaDataTypesQR-2.pdf


If you do not like xsd...

Simply define your own datatypes… @prefix b: <hIp://www.R4SC.net/building#> . @prefix c: <hIp://www.R4SC.net/city#> . @prefix dt: < hIp://www.R4SC.net/todaysdts#> . <hIp://www.R4SC.net/today#building_1>

b:hasName “Our summer school building”^^dt:myTypeOfString


Index


–  URIs –  RDF Statements –  Literals –  Collec2ons and containers




39


RepeaYng properYes

•  I have a property that can have mulYple values, now what? – SoluYon 1: Simply repeat the property of the resource mulYple Ymes.

– SoluYon 2: Use a structured value for a literal – SoluYon 3: Use an RDF Container (Sequence, Bag, or Alt) or CollecYon (RDF List)

http://patterns.dataincubator.org/book/repeated-property.html


Example for soluYon 1: simply repeaYng property

@prefix b: <hIp://www.R4SC.net/building#> . @prefix rdf: <hIp://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#> . <hIp://www.R4SC.net/today#room_1>

b:hasPersonInside <hIp://www.R4SC.net/today#PieterPauwels> , <hIp://www.R4SC.net/today#RaulGarciaCastro> , <hIp://www.R4SC.net/

today#AsuncionGomezPerez> , <hIp://www.R4SC.net/today#MariaPovedaVillalon> , <hIp://www.R4SC.net/today#FilipRadulovic> .


Example for soluYon 2: Use a structured value for a literal


b:hasPeopleInside “IRECOGNIZETHIS:PieterPauwels; IRECOGNIZETHIS: RaulGarciaCastro; IRECOGNIZETHIS:AsuncionGomezPerez; IRECOGNIZETHIS: MariaPovedaVillalon; IRECOGNIZETHIS: FilipRadulovic”

=> NOT recommended!!


Example for soluYon 3


b:hasPeopleInside ( <hIp://www.R4SC.net/today#PieterPauwels> <hIp://www.R4SC.net/today#RaulGarciaCastro> <hIp://www.R4SC.net/

today#AsuncionGomezPerez> <hIp://www.R4SC.net/today#MariaPovedaVillalon> <hIp://www.R4SC.net/today#FilipRadulovic> )


So, what are our opYons for soluYon 3?

•  Apart from resources and literals, it is also possible to describe ‘containers’ and ‘collecYons’

•  Containers – Bags – Sequences – Alt

•  CollecYons – Lists

used to describe groups that can ONLY contain the specified members

used to describe an open groups of things (unknown length)


Bags – Seqs – Alts ??

•  Bag –  Unordered –  Resources or literals –  Duplicate values are permiIed

•  Sequence (Seq) –  Ordered –  Resources or literals –  Duplicate values are permiIed

•  AlternaYve (Alt) –  Unordered –  Resources or literals –  Alterna2ves for a single property value (cfr. language alternaYves)

These are the convenYons / they are ‘just’ convenYons


List

•  List – Ordered – Resources or literals – Duplicate values are permiIed – Closed collecYon – length of list is known

•  So, idenYcal to a sequence, except that the collecYon is closed: only the listed items are in the List, nothing else


Back to our example


b:hasPeopleInside ( <hIp://www.R4SC.net/today#PieterPauwels> <hIp://www.R4SC.net/today#RaulGarciaCastro> <hIp://www.R4SC.net/

today#AsuncionGomezPerez> <hIp://www.R4SC.net/today#MariaPovedaVillalon> <hIp://www.R4SC.net/today#FilipRadulovic> )


The downside of soluYon 3 <?xml version="1.0" encoding="UTF-‐8"?> <rdf:RDF xmlns:b="hIp://www.R4SC.net/building#" xmlns:rdf="hIp://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#"> <rdf:DescripYon rdf:about="hIp://www.R4SC.net/today#room_1"> <b:hasPeopleInside rdf:nodeID="fabfea5436e794e259b04593dadf0c9f8b1"/> </rdf:DescripYon> <rdf:DescripYon rdf:nodeID="fabfea5436e794e259b04593dadf0c9f8b4"> <rdf:first rdf:resource="hIp://www.R4SC.net/today#MariaPovedaVillalon"/> <rdf:rest rdf:nodeID="fabfea5436e794e259b04593dadf0c9f8b5"/> </rdf:DescripYon> <rdf:DescripYon rdf:nodeID="fabfea5436e794e259b04593dadf0c9f8b5"> <rdf:first rdf:resource="hIp://www.R4SC.net/today#FilipRadulovic"/> <rdf:rest rdf:resource="hIp://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#nil"/> </rdf:DescripYon> <rdf:DescripYon rdf:nodeID="fabfea5436e794e259b04593dadf0c9f8b2"> <rdf:first rdf:resource="hIp://www.R4SC.net/today#RaulGarciaCastro"/> <rdf:rest rdf:nodeID="fabfea5436e794e259b04593dadf0c9f8b3"/> </rdf:DescripYon> <rdf:DescripYon rdf:nodeID="fabfea5436e794e259b04593dadf0c9f8b1"> <rdf:first rdf:resource="hIp://www.R4SC.net/today#PieterPauwels"/> <rdf:rest rdf:nodeID="fabfea5436e794e259b04593dadf0c9f8b2"/> </rdf:DescripYon> <rdf:DescripYon rdf:nodeID="fabfea5436e794e259b04593dadf0c9f8b3"> <rdf:rest rdf:nodeID="fabfea5436e794e259b04593dadf0c9f8b4"/> <rdf:first rdf:resource="hIp://www.R4SC.net/today#AsuncionGomezPerez"/> </rdf:DescripYon> </rdf:RDF>

Blank nodes Elaborate and complex descrip2on


RepeaYng properYes

•  I have a property that can have mulYple values, now what? – SoluYon 1: Simply repeat the property of the resource mulYple Ymes. RepeaYng properYes is the simplest approach to handling mulY-‐valued relaYons. The alternaYves all have their downsides.

– SoluYon 2: Use a structured value for a literal – SoluYon 3: Use an RDF Container (Sequence, Bag, or Alt) or CollecYon (RDF List)

http://patterns.dataincubator.org/book/repeated-property.html


Wait a second…

Did you say ‘blank nodes’?


What are blank nodes?

•  Blank nodes are nodes that do not have URIs –  No URI -‐> no semanYcs really -‐> unstable and unreliable

•  They are usually represented as: _:1, _:city, _:thiscanbeanythingyouwishfor, _:8936fazGUID, …

•  This representaYon is typically generated on-‐the-‐fly so that it is unique within the scope in which an RDF graph is opened – When opening this RDF graph the following day, even in the same scope, enYrely different names might be generated

–  Unstable and unreliable

51


So, why do we use these blank nodes?

•  Simply because it is hard to give everything an explicit name, this is not always wanted / desirable

•  For example:

@prefix b: <hIp://www.R4SC.net/building#> . @prefix c: <hIp://www.R4SC.net/city#> . @prefix region: <hIp://www.R4SC.net/region#> . <hIp://www.R4SC.net/today#building_1>

b:hasRoom <hIp://www.R4SC.net/today#room_1> ; b:hasName “Our summer school building"; c:partOfCity <hIp://ciYes.com/#cercedilla> ; c:partOfRegion [ region:locaYon “NorthOfMadrid”; region:regiontype “Forest”]

•  Likewise, people do not intend to define names for all kinds of groups of things -‐> hence a lot of blank nodes in descripYons of collecYons and containers

52

Blank node


Index






53


Data integraYon now possible

MyBuilding CiYes


We already integrated datasets!


Linked Open Data Cloud

•  hIp://lod-‐cloud.net/

•  datasets that have been published in Linked Data format, by contributors to the Linking Open Data community project and other individuals and organisaYons

•  based on metadata collected and curated by contributors to the Data Hub as well as on metadata extracted from a crawl of the Linked Data web conducted in April 2014

•  AIribuYon: Linking Open Data cloud diagram 2014, by Max Schmachtenberg, ChrisYan Bizer, Anja Jentzsch and Richard Cyganiak. hIp://lod-‐cloud.net/


lod-‐cloud.net

http://lod-cloud.net (Last version: 2014-08-30)


History of the LOD

http://lod-cloud.net


LOD as of May 2007


LOD as of March 2009


!!!!AdverYsement break!!!!

RDF(S) and SPARQL Pieter Pauwels

More to come aser the break


!!!!AdverYsement break!!!!

hIp://ldac-‐2015.bwk.tue.nl/


Before the break


LOD as of August 2014


Circle sizes and arrow fonts

•  Depending on the size of the dataset and the number of triples between datasets, the layout in the LOD cloud schema is different.


Data integraYon now possible

MyBuilding CiYes


Status and staYsYcs

•  CumulaYve stats: hIp://stats.lod2.eu/ •  State of the LOD cloud 2014: hIp://linkeddatacatalog.dws.informaYk.uni-‐mannheim.de/state/ •  State of the LOD cloud 2011: hIp://lod-‐cloud.net/state/


Triple counts

hIp://stats.lod2.eu/


Stats -‐ Datasets by topical domain

hIp://linkeddatacatalog.dws.informaYk.uni-‐mannheim.de/state/

Topic Datasets % Government 183 18.05%

PublicaYons 96 9.47%

Life sciences 83 8.19%

User-‐generated content 48 4.73%

Cross-‐domain 41 4.04%

Media 22 2.17%

Geographic 21 2.07%

Social web 520 51.28%

Total 1014


Stats -‐ CategorizaYon by number of linked datasets

Number of linked datasets Number of datasets more than 10 79 (7.79%)

6 to 10 81 (7.99%)

5 31 (3.06%)

4 42 (4.14%)

3 54 (5.33%)

2 106 (10.45%)

1 176 (17.36%)

0 445 (43.89%)

hIp://linkeddatacatalog.dws.informaYk.uni-‐mannheim.de/state/


Can my dataset be included?

First, make sure that you publish data according to the Linked Data principles. We interpret this as: •  There must be resolvable h+p:// (or h+ps://) URIs. •  They must resolve, with or without content negoYaYon,

to RDF data in one of the popular RDF formats (RDFa, RDF/XML, Turtle, N-‐Triples).

•  The dataset must contain at least 1000 triples. •  The dataset must be connected via RDF links to a dataset

that is already in the diagram. This means, either your dataset must use URIs from the other dataset, or vice versam. We arbitrarily require at least 50 links.

•  Access of the en=re dataset must be possible via RDF crawling, via an RDF dump, or via a SPARQL endpoint.

Then, add it to the Data Hub and request to be included


The resolvable URIs

Hold on, what do you mean, ‘resolvable’?


Reminder: What is a URI?

•  URI stands for Unique Resource IdenYfier •  Purpose: Obtain globally unique idenYfiers, so that informaYon

can be exchanged globally. •  Structure:


•  Namespace needed to avoid name conflicts with tags of the same name: other tags with the name “building_1" can be defined with other namespace URIs, and an RDF reader would sYll be able to tell that they were different properYes even though they had the same tag name.

73

Namespace Name


What do you mean… resolvable?

•  A resolvable URI is: “A URI whose resource has one or more representa=ons available via invoking HTTP GET on the URI” (source: hIp://www.w3.org/TR/2010/WD-‐sparql11-‐hIp-‐rdf-‐update-‐20100126/)

74

hIp://www.w3.org/TR/cooluris/#oldweb


Dereferencing URIs

hIp://wifo5-‐03.informaYk.uni-‐mannheim.de/bizer/pub/LinkedDataTutorial/


So, you are now ready to publish here


Note: the O in LOD

•  This does NOT mean that RDF is “OPEN” by default

•  Most datasets in the LOD cloud have licence informaYon aIached

•  This does NOT mean that RDF is “OPEN” by default


Index






78


What did we do so far?





79



80



The RDF namespace

@prefix rdf: h]p://www.w3.org/1999/02/22-‐

rdf-‐syntax-‐ns#


The first few lines


We have actually already used it

<?xml version="1.0" encoding="UTF-‐8"?> <rdf:RDF xmlns:b="hIp://www.R4SC.net/building#" xmlns:c="hIp://www.R4SC.net/city#" xmlns:rdf="hIp://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#"> <rdf:DescripYon rdf:about="hIp://www.R4SC.net/today#building_1"> <c:partOfCity rdf:resource="hIp://ciYes.com/#cercedilla"/> <b:hasName>Our summer school building</b:hasName> <b:hasRoom rdf:resource="hIp://www.R4SC.net/today#room_1"/> </rdf:DescripYon> <rdf:DescripYon rdf:about="hIp://ciYes.com/#cercedilla"> <c:hasName>Cercedilla</c:hasName> <c:closeToCity rdf:resource="hIp://ciYes.com/#madrid"/> </rdf:DescripYon> </rdf:RDF>

83


Need for structured vocabularies

•  RDF graphs -‐> could be anything •  Need for semanYcs / structured vocabularies

⇒  RDFSchema (RDFS) ⇒  Web Ontology Language (OWL)



85



The RDFS namespace

@prefix rdfs: h]p://www.w3.org/2000/01/rdf-‐schema#


Example TTL graph

-‐> ambiguous / close to meaningless


Example vocabulary in TTL @prefix rdfs: <hIp://www.w3.org/2000/01/rdf-‐schema#> . @prefix rdf: <hIp://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#> . @prefix b: <hIp://www.R4SC.net/building#> . @prefix c: <hIp://www.R4SC.net/city#> . b:InfrastructuralElement

rdf:type rdfs:Class . b:Building

rdf:type rdfs:Class ; rdfs:subClassOf b:InfrastructuralElement .

b:hasRoom

rdf:type rdf:Property ; rdfs:range b:Room ; rdfs:domain b:Building .

89


The same thing in RDF/XML

<?xml version="1.0" encoding="u�-‐8"?> <rdf:RDF xmlns:rdf="hIp://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#" xmlns:rdfs="hIp://www.w3.org/2000/01/rdf-‐schema#"> <rdf:Property rdf:about="hIp://www.R4SC.net/building#hasRoom"> <rdfs:domain rdf:resource="hIp://www.R4SC.net/building#Building"/> <rdfs:range rdf:resource="hIp://www.R4SC.net/building#Room"/> </rdf:Property> <rdfs:Class rdf:about="hIp://www.R4SC.net/building#InfrastructuralElement"/> <rdfs:Class rdf:about="hIp://www.R4SC.net/building#Building"> <rdfs:subClassOf rdf:resource="hIp://www.R4SC.net/building#InfrastructuralElement"/> </rdfs:Class> </rdf:RDF>

90


Combining instances and vocabulary

@prefix rdfs: <hIp://www.w3.org/2000/01/rdf-‐schema#> . @prefix rdf: <hIp://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#> . @prefix b: <hIp://www.R4SC.net/building#> . @prefix c: <hIp://www.R4SC.net/city#> . b:InfrastructuralElement

rdf:type rdfs:Class . b:Building

rdf:type rdfs:Class ; rdfs:subClassOf b:InfrastructuralElement .

b:hasRoom

rdf:type rdf:Property ; rdfs:range b:Room ; rdfs:domain b:Building .

91


b:hasRoom <hIp://www.R4SC.net/today#room_1>; b:hasName “Our summer school building"; c:partOfCity <hIp://ciYes.com/#cercedilla> .




Example TTL graph

-‐> unambiguous / meaningful semanYcs


Index






93



94



So, it’s also just an RDF graph…

95

http://www.w3.org/DesignIssues/diagrams/n3/venn

We s2ck to Turtle today

Let’s just quietly extend towards SPARQL as well


Index






96


What is SPARQL

•  SPARQL stands for SPARQL Protocol and RDF Query Language •  SPARQL is a Query Language •  Find the W3C RecommendaYon page:

hIp://www.w3.org/TR/rdf-‐sparql-‐query/ –  Used to express queries across diverse data sources, whether the data is

stored naYvely as RDF or viewed as RDF via middleware. –  SPARQL contains capabiliYes for querying required and opYonal graph

paIerns along with their conjuncYons and disjuncYons. –  SPARQL supports extensible value tesYng and constraining queries by

source RDF graph. –  The results of SPARQL queries can be results sets or RDF graphs.


The inspiraYon: SQL

select A1, A2, ..., An from r1, r2, ..., rm where P


SPARQL template

prefix a:… select concepts from datasources where { statements } order by …


Structure of a SPARQL query

•  Prefix declaraYons Used to abbreviate URIs

•  Dataset definiYon Used to state what RDF graph(s) are being queried

•  A result clause Used to idenYfy what informaYon to return from the query

•  The query paIern Used to specify what to query for in the underlying dataset

•  Query modifiers, slicing, ordering, and otherwise Used to rearrange query results (post-‐processing)


Let’s query our example graph


Example SPARQL Query

PREFIX b: <hIp://www.R4SC.net/building#> . PREFIX c: <hIp://www.R4SC.net/city#> . SELECT ?city2 WHERE {

?b b:hasRoom <hIp://www.R4SC.net/today#room_1> . ?b c:partOfCity ?city . ?city c:closeToCity ?city2

}

variable

Regular RDF statements

Regular RDF prefix declara2ons


Processing the WHERE statement secYon

•  A pa+ern is matched against the RDF data •  “find a set of bindings such that the subs=tu=on of variables for values creates a triple that is in the set of triples making up the graph”

•  Source: hIp://www.w3.org/2004/Talks/17Dec-‐sparql/QueryLang1/all.html


Graph matching


The Query Result

city2

<hIp://ciYes.com/#madrid>


Index






106


Example SPARQL endpoint on DBPedia

The HTTP Address of the endpoint

The soiware used in the server to store the triples (cfr. DBMS)

Diverse op2ons to set


Try it

Try it out on the DBPedia dataset:

hIp://dbpedia.org/sparql Or even beIer: host one yourself and make it available

108


Index




–  The basis –  The SPARQL endpoint –  More details


109


Matching literals (1) RDF data: @prefix b: <hIp://www.R4SC.net/building#> . @prefix people: <hIp://www.R4SC.net/people#> . @prefix xsd: <hIp://www.w3.org/2001/XMLSchema#> . <hIp://www.R4SC.net/today#room_1>

b:hasPersonInside "Pieter"@en . <hIp://www.R4SC.net/today#restaurant>

b:hasPersonInside "Raul"^^xsd:string . <hIp://www.R4SC.net/today#airport>

b:hasPersonInside "Leandro"^^people:keynotespeaker . Query SELECT ?v WHERE { ?v ?p "Pieter" } Result { }





b:hasPersonInside "Leandro"^^people:keynotespeaker . Query SELECT ?v WHERE { ?v ?p "Pieter"@en} Result { <hIp://www.R4SC.net/today#room_1> }





b:hasPersonInside "Leandro"^^people:keynotespeaker . Query SELECT ?v WHERE { ?v ?p "Leandro"^^< hIp://www.R4SC.net/people#keynotespeaker > } Result { <hIp://www.R4SC.net/today#airport > }


Querying blank nodes

RDF data: @prefix b: <hIp://www.R4SC.net/building#> . _:room1 b:hasPersonInside “Pieter" . _:room2 b:hasPersonInside “Raul" . Query PREFIX b: <hIp://www.R4SC.net/building#> SELECT ?x ?name WHERE { ?x b:hasPersonInside ?name } Result

x name

_:c "Pieter"

_:d "Leandro"

x name

_:r "Pieter"

_:s "Leandro" …


CONSTRUCT queries RDF data: @prefix b: <hIp://www.R4SC.net/building#> . @prefix : <hIp://www.R4SC.net/today#> . _:a b:presenterName “Pieter" . _:b b:presenterName “Raul" . :room1 b:hasPersonInside _:a . :room1 b:hasPersonInside “Raul" . :room1 rdf:type b:R4SCPresentaYonRoom Query PREFIX b: <hIp://www.R4SC.net/building#> WHERE { ?x rdf:type b:R4SCPresentaYonRoom . ?x: b:hasPersonInside ?z . ?z b:presenterName ?name } CONSTRUCT { ?x b:hasR4SCPresenter ?name } Result @prefix b: <hIp://www.R4SC.net/building#> . @prefix : <hIp://www.R4SC.net/today#> . :room1 b:hasR4SCPresenter “Pieter” . :room1 b:hasR4SCPresenter “Raul”


SPARQL Filters RDF data: @prefix b: <hIp://www.R4SC.net/building#> . @prefix : <hIp://www.R4SC.net/today#> . :room_1 b:hasPresentaYonTitle “RDF(S) and SPARQL" . :room_1 b:hasPeopleInside 28 . :room_2 b:hasPresentaYonTitle “Handson session RDF(S) and SPARQL" . :room_2 b:hasPeopleInside 23 . Query @prefix b: <hIp://www.R4SC.net/building#> . SELECT ?Ytle WHERE { ?x b:hasPresentaYonTitle ?Ytle

FILTER regex(?Ytle, "^Hands") } Result

title

"Handson session RDF(S) and SPARQL"

Many possibili2es: string matching, value restric2ons (greaterThan, etc.), DateTime restric2ons, …


OPTIONAL keyword RDF data: @prefix b: <hIp://www.R4SC.net/building#> . @prefix : <hIp://www.R4SC.net/today#> . :room_1 b:hasPresentaYonTitle “RDF(S) and SPARQL" . :room_1 b:hasPeopleInside 28 . :room_2 b:hasPresentaYonTitle “Handson session RDF(S) and SPARQL" . :room_2 b:hasPeopleInside 23 . Query @prefix b: <hIp://www.R4SC.net/building#> . SELECT ?Ytle ?aIendees WHERE { ?x b:hasPresentaYonTitle ?Ytle . OPTIONAL { ?x b:hasPeopleInside ?aIendees. FILTER (?aIendees > 25) } } Result

title attendees

"RDF(S) and SPARQL" 28

"Handson session RDF(S) and SPARQL"

If there is a match, give the op2onal data, otherwise give the required data


LIMIT Keyword RDF data: @prefix b: <hIp://www.R4SC.net/building#> . @prefix rdf: <hIp://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#> . <hIp://www.R4SC.net/today#room_1>

b:hasPersonInside “PieterPauwels" , “RaulGarciaCastro" , “AsuncionGomezPerez" , “MariaPovedaVillalon", “FilipRadulovic" .

Query PREFIX b: <hIp://www.R4SC.net/building#> SELECT ?name WHERE { ?x b:hasPersonInside ?name } LIMIT 2 Result

name

“PieterPauwels"

“RaulGarciaCastro"


ORDER BY RDF data: @prefix b: <hIp://www.R4SC.net/building#> . @prefix rdf: <hIp://www.w3.org/1999/02/22-‐rdf-‐syntax-‐ns#> . <hIp://www.R4SC.net/today#room_1>

b:hasPersonInside “PieterPauwels" , “RaulGarciaCastro" , “AsuncionGomezPerez" , “MariaPovedaVillalon", “FilipRadulovic" .

Query PREFIX b: <hIp://www.R4SC.net/building#> SELECT ?name WHERE { ?x b:hasPersonInside ?name } LIMIT 2 ORDER BY DESC(?name) Result

name

“RaulGarciaCastro"

“PieterPauwels"


DISTINCT Keyword RDF data: @prefix b: <hIp://www.R4SC.net/building#> . @prefix : <hIp://www.R4SC.net/today#> . :room_1 b:hasPresentaYon [ b:hasPresentaYonTitle “RDF(S) and SPARQL" ] . :room_1 b:hasPresentaYon [ b:hasPresentaYonTitle “Handson session Generate your RDF”; b:startsAt “14:30:00”^^xsd:Yme ] . :room_1 b:hasPresentaYon [ b:hasPresentaYonTitle “Handson session Generate your RDF”; b:startsAt “17:00:00”^^xsd:Yme ] . Query PREFIX b: < hIp://www.R4SC.net/building# > SELECT DISTINCT ?Ytle WHERE { ?x b:hasPresentaYonTitle ?Ytle} Result

title

“RDF(S) and SPARQL"

“Handson session Generate your RDF"


UNION Keyword RDF data: @prefix b: <hIp://www.R4SC.net/building#> . @prefix : <hIp://www.R4SC.net/today#> . :room_1 b:hasPresentaYon [ b:hasPresentaYonTitle “RDF(S) and SPARQL" ] . :room_1 b:hasPresentaYon [ b:hasPresentaYonTitle “Handson session Generate your RDF”; b:startsAt “14:30:00”^^xsd:Yme ] . :room_1 b:hasPresentaYon [ b:hasPresentaYonTitle “Handson session Generate your RDF”; b:startsAt “17:00:00”^^xsd:Yme ] . _:x1 b:presentaYon “Linking Data” . Query @prefix b: <hIp://www.R4SC.net/building#> . @prefix : <hIp://www.R4SC.net/today#> . SELECT DISTINCT ?Ytle_1 ?Ytle_2 WHERE { { ?p b:hasPresentaYonTitle ?Ytle_1 } UNION { ?p1 b:presentaYon ?Ytle_2 } }

title

“RDF(S) and SPARQL"

“Handson session Generate your RDF"

“Linking Data”

Result


But well, the only way to learn it…

Try it out, for example, on the DBPedia dataset:

hIp://dbpedia.org/sparql Or even beIer: host one yourself and make it available

121


Index






122



123




1st Summer School on Smart Ci2es and Linked Open Data (LD4SC-‐15)

Thank you for your aIenYon!

[email protected]

rdf(s) and sparql

Science

spain ld4scsummerschool

spain rdfgraphs

spain connecyngtriples

spain syntaxesforserialisayon

spain theresult

spain atriple

spain thesemanycwebstack

spain expressivenessofsyntaxes