Summer School LD4SC 2015 - RDF(S) and SPARQL

LD4SC Summer School7th - 12th June, Cercedilla, Spain

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

RDF(S) and SPARQL

Pieter Pauwels, Ghent University

The cool and awesome intro movies

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

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

– URIs– RDF Statements– Literals– Collections and containers

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

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

• Concluding Overview

RDF graphs, what are they

RDF graphs are DIRECTED, LABELLED GRAPHS

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)

Relational databases (cfr. MySQL, SQLServer)

RDF graphs are DIRECTED, LABELLED GRAPHS

A triple

Triple

SUBJECT OBJECTPREDICATE

Connecting Triples

SUBJECT OBJECTPREDICATE

OBJECT

PREDICATE

OBJECT

PREDICATE

OBJECTPREDICATE

The result: an RDF graph

LABELLED

DIRECTED

Triple

That is it: simple directed labelled graphs, always remember

Talking the RDF language

• RDF stands for Resource Description 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 information, sensors, … anything goes

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

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

easily used

usually

-> standardisation

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

The Semantic Web stack

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

Syntaxes for serialisation

Triple

RDF/XML

Turtle (TTL)

Notation-3 (N3)

Expressiveness of syntaxes

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

We stick to Turtle today

Example TTL file

@prefix b: <http://www.R4SC.net/building#> . @prefix c: <http://www.R4SC.net/city#> .

<http://www.R4SC.net/today#building_1> b:hasRoom <http://www.R4SC.net/today#room_1> ; b:hasName “Our summer school building"; c:partOfCity <http://cities.com/#cercedilla> .

<http://cities.com/#cercedilla> c:closeToCity <http://cities.com/#madrid> ;c:hasName “Cercedilla” .

Example TTL graph

The same thing in RDF/XML

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

Convert to different syntaxes

Convert to/from syntaxes:

http://rdf-translator.appspot.com/

Or simply build and use your own software tool

Uniform Resource Identifiers

URIURI

What is a URI?

• URI stands for Uniform Resource Identifier• Purpose: Obtain globally unique identifiers, so that information

can be exchanged globally.• Structure:

<http://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 still be able to tell that they were different properties even though they had the same tag name.

Namespace Name

Full version of the URIs

<http://www.R4SC.net/today#building_1><http://www.R4SC.net/today#room_1>

<http://www.R4SC.net/building#hasRoom ><http://www.R4SC.net/building#hasName >

<http://www.R4SC.net/city#partOfCity><http://www.R4SC.net/city#closeToCity><http://www.R4SC.net/city#hasName>

<http://cities.com/#cercedilla><http://cities.com/#madrid>

Example TTL file

Prefixed URIs

@prefix b: <http://www.R4SC.net/building#> . @prefix c: <http://www.R4SC.net/city#> . @prefix bi: <http://www.R4SC.net/today#> . @prefix ci: < http://cities.com/# > .

bi:building_1bi:room_1

b:hasRoomb:hasName

c:partOfCityc:closeToCityc:hasName

ci:madridci:cercedilla

TTL file with fully qualified names

<http://www.R4SC.net/today#building_1> <http://www.R4SC.net/building#hasRoom >

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

<http://cities.com/#cercedilla> <http://www.R4SC.net/city#closeToCity > <http://cities.com/#madrid> ;<http://www.R4SC.net/city#hasName > “Cercedilla” .

-> prefixes increase readibility

Statements

Statement

Statement follows triple structure

<http://www.R4SC.net/today#building_1><http://www.R4SC.net/city#partOfCity > <http://cities.com/#cercedilla> .

Triple

<http://www.R4SC.net/

today#building_1>

<http://cities.com/#cercedilla>

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

Combining statements

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

<http://cities.com/#cercedilla> <http://www.R4SC.net/city#closeToCity > <http://cities.com/#madrid> ;<http://www.R4SC.net/city#hasName > “Cercedilla” .

Same subject

AND [next statement]

Same subject

Same subjectAND [next statement]

, Same subject, same predicate

List of all statements

<http://www.R4SC.net/today#room_1> .

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

<http://www.R4SC.net/today#building_1> <http://www.R4SC.net/city#partOfCity > <http://cities.com/#cercedilla> .

<http://cities.com/#cercedilla> <http://www.R4SC.net/city#closeToCity > <http://cities.com/#madrid> .

<http://cities.com/#cercedilla> <http://www.R4SC.net/city#hasName > “Cercedilla” .

Statements

Statement

Recap on the URIs

URIURI

Literals in the statements

<http://www.R4SC.net/today#room_1> .

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

<http://www.R4SC.net/today#building_1> <http://www.R4SC.net/city#partOfCity > <http://cities.com/#cercedilla> .

<http://cities.com/#cercedilla> <http://www.R4SC.net/city#closeToCity > <http://cities.com/#madrid> .

<http://cities.com/#cercedilla> <http://www.R4SC.net/city#hasName > “Cercedilla” .

Literal

Conventional representation / distinction from regular resources

Resource

Literal

Similar yet distinct

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

<http://www.R4SC.net/today#building_1> b:hasName “Our summer school building” ,

“Our summer school building”@en , “Our summer school building”^^xsd:string

Untyped

Literal with language setting Referring to type

within specific namespace

What is available in xsd

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

What is available in xsd

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

If you do not like xsd...

Simply define your own datatypes…

@prefix b: <http://www.R4SC.net/building#> . @prefix c: <http://www.R4SC.net/city#> . @prefix dt: < http://www.R4SC.net/todaysdts#> .

<http://www.R4SC.net/today#building_1> b:hasName “Our summer school building”^^dt:myTypeOfString

Repeating properties

• I have a property that can have multiple values, now what?– Solution 1: Simply repeat the property of the

resource multiple times. – Solution 2: Use a structured value for a literal– Solution 3: Use an RDF Container (Sequence, Bag,

or Alt) or Collection (RDF List)

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

Example for solution 1: simply repeating property

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

<http://www.R4SC.net/today#room_1> b:hasPersonInside <http://www.R4SC.net/today#PieterPauwels> ,

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

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

<http://www.R4SC.net/today#room_1> b:hasPeopleInside “IRECOGNIZETHIS:PieterPauwels; IRECOGNIZETHIS:

RaulGarciaCastro; IRECOGNIZETHIS:AsuncionGomezPerez; IRECOGNIZETHIS: MariaPovedaVillalon; IRECOGNIZETHIS: FilipRadulovic”

=> NOT recommended!!

Example for solution 3

<http://www.R4SC.net/today#room_1> b:hasPeopleInside ( <http://www.R4SC.net/today#PieterPauwels>

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

So, what are our options for solution 3?

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

• Containers– Bags– Sequences– Alt

• Collections– 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 permitted

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

• Alternative (Alt)– Unordered– Resources or literals– Alternatives for a single property value (cfr. language alternatives)These are the conventions / they are ‘just’ conventions

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

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

Back to our example

<http://www.R4SC.net/today#room_1> b:hasPeopleInside ( <http://www.R4SC.net/today#PieterPauwels>

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

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

Blank nodesElaborate and complex description

Repeating properties

• I have a property that can have multiple values, now what?– Solution 1: Simply repeat the property of the

resource multiple times. Repeating properties is the simplest approach to handling multi-valued relations. The alternatives all have their downsides.

– Solution 2: Use a structured value for a literal– Solution 3: Use an RDF Container (Sequence, Bag,

or Alt) or Collection (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 semantics really -> unstable and unreliable

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

• This representation 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, entirely different names might be generated– Unstable and unreliable

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: <http://www.R4SC.net/building#> . @prefix c: <http://www.R4SC.net/city#> . @prefix region: <http://www.R4SC.net/region#> .

<http://www.R4SC.net/today#building_1> b:hasRoom <http://www.R4SC.net/today#room_1> ; b:hasName “Our summer school building"; c:partOfCity <http://cities.com/#cercedilla> ;c:partOfRegion [ region:location “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 descriptions of collections and containers

Blank node

Data integration now possible

MyBuilding Cities

We already integrated datasets!

Linked Open Data Cloud

• http://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 organisations

• 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

• Attribution: Linking Open Data cloud diagram 2014, by Max Schmachtenberg, Christian Bizer, Anja Jentzsch and Richard Cyganiak. http://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

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RDF(S) and SPARQLPieter Pauwels

More to come after the break

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http://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 integration now possible

MyBuilding Cities

Status and statistics

• Cumulative stats:http://stats.lod2.eu/ • State of the LOD cloud 2014: http://linkeddatacatalog.dws.informatik.uni-mannheim.de/state/• State of the LOD cloud 2011: http://lod-cloud.net/state/

Triple counts

http://stats.lod2.eu/

Stats - Datasets by topical domain

http://linkeddatacatalog.dws.informatik.uni-mannheim.de/state/

Topic Datasets %Government 183 18.05%

Publications 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 - Categorization by number of linked datasets

Number of linked datasets Number of datasetsmore 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%)

http://linkeddatacatalog.dws.informatik.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 http:// (or https://) URIs.• They must resolve, with or without content negotiation, 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 entire 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 Identifier• Purpose: Obtain globally unique identifiers, so that information

can be exchanged globally.• Structure:

<http://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 still be able to tell that they were different properties even though they had the same tag name.

Namespace Name

What do you mean… resolvable?

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

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

Dereferencing URIs

http://wifo5-03.informatik.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 information attached

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

What did we do so far?

The RDF namespace

@prefix rdf: http://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="http://www.R4SC.net/building#" xmlns:c="http://www.R4SC.net/city#" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> <rdf:Description rdf:about="http://www.R4SC.net/today#building_1"> <c:partOfCity rdf:resource="http://cities.com/#cercedilla"/> <b:hasName>Our summer school building</b:hasName> <b:hasRoom rdf:resource="http://www.R4SC.net/today#room_1"/> </rdf:Description> <rdf:Description rdf:about="http://cities.com/#cercedilla"> <c:hasName>Cercedilla</c:hasName> <c:closeToCity rdf:resource="http://cities.com/#madrid"/> </rdf:Description></rdf:RDF>

Need for structured vocabularies

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

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

The RDFS namespace

@prefix rdfs: http://www.w3.org/2000/01/rdf-schema#

Example TTL graph

-> ambiguous / close to meaningless

Example vocabulary in TTL

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

b:InfrastructuralElementrdf:type rdfs:Class .

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

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

The same thing in RDF/XML

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

Combining instances and vocabulary

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

b:InfrastructuralElementrdf:type rdfs:Class .

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

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

<http://www.R4SC.net/today#building_1> b:hasRoom <http://www.R4SC.net/today#room_1>; b:hasName “Our summer school building"; c:partOfCity <http://cities.com/#cercedilla> .

Example TTL graph

-> unambiguous / meaningful semantics

So, it’s also just an RDF graph…

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

We stick to Turtle today

Let’s just quietly extend towards SPARQL as well

What is SPARQL

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

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

stored natively as RDF or viewed as RDF via middleware. – SPARQL contains capabilities for querying required and optional graph

patterns along with their conjunctions and disjunctions. – SPARQL supports extensible value testing and constraining queries by

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

The inspiration: SQL

select A1, A2, ..., Anfrom r1, r2, ..., rmwhere P

SPARQL template

prefix a:…select conceptsfrom datasourceswhere { statements }order by …

Structure of a SPARQL query

• Prefix declarationsUsed to abbreviate URIs

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

• A result clauseUsed to identify what information to return from the

query• The query pattern

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: <http://www.R4SC.net/building#> .PREFIX c: <http://www.R4SC.net/city#> .

SELECT ?city2 WHERE {

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

variable

Regular RDF statements

Regular RDF prefix declarations

Processing the WHERE statement section

• A pattern is matched against the RDF data• “find a set of bindings such that the substitution of variables for values creates a triple that is in the set of triples making up the graph”

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

Graph matching

The Query Result

<http://cities.com/#madrid>

Example SPARQL endpoint on DBPedia

The HTTP Address of the endpoint

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

Diverse options to set

Try it

Try it out on the DBPedia dataset:

http://dbpedia.org/sparql

Or even better: host one yourself and make it available

– The basis– The SPARQL endpoint– More details

Matching literals (1)

RDF data:@prefix b: <http://www.R4SC.net/building#> . @prefix people: <http://www.R4SC.net/people#> . @prefix xsd: <http://www.w3.org/2001/XMLSchema#> . <http://www.R4SC.net/today#room_1>

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

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

b:hasPersonInside "Leandro"^^people:keynotespeaker .

QuerySELECT ?v WHERE { ?v ?p "Pieter" }

Result{ }

QuerySELECT ?v WHERE { ?v ?p "Pieter"@en}

Result{ <http://www.R4SC.net/today#room_1> }

QuerySELECT ?v WHERE { ?v ?p "Leandro"^^< http://www.R4SC.net/people#keynotespeaker > }

Result{ <http://www.R4SC.net/today#airport > }

Querying blank nodes

RDF data:@prefix b: <http://www.R4SC.net/building#> .

_:room1 b:hasPersonInside “Pieter" . _:room2 b:hasPersonInside “Raul" .

QueryPREFIX b: <http://www.R4SC.net/building#> SELECT ?x ?nameWHERE { ?x b:hasPersonInside ?name }

Resultx name

_:c "Pieter"

_:d "Leandro"

x name

_:r "Pieter"

_:s "Leandro"…

CONSTRUCT queriesRDF data:@prefix b: <http://www.R4SC.net/building#> .@prefix : <http://www.R4SC.net/today#> ._:a b:presenterName “Pieter" ._:b b:presenterName “Raul" .:room1 b:hasPersonInside _:a . :room1 b:hasPersonInside “Raul" .:room1 rdf:type b:R4SCPresentationRoom

QueryPREFIX b: <http://www.R4SC.net/building#> WHERE { ?x rdf:type b:R4SCPresentationRoom . ?x: b:hasPersonInside ?z . ?z b:presenterName ?name }CONSTRUCT { ?x b:hasR4SCPresenter ?name }

Result@prefix b: <http://www.R4SC.net/building#> .@prefix : <http://www.R4SC.net/today#> .:room1 b:hasR4SCPresenter “Pieter” .:room1 b:hasR4SCPresenter “Raul”

SPARQL FiltersRDF data:@prefix b: <http://www.R4SC.net/building#> .@prefix : <http://www.R4SC.net/today#> .:room_1 b:hasPresentationTitle “RDF(S) and SPARQL" .:room_1 b:hasPeopleInside 28 .:room_2 b:hasPresentationTitle “Handson session RDF(S) and SPARQL" .:room_2 b:hasPeopleInside 23 .

Query@prefix b: <http://www.R4SC.net/building#> .SELECT ?titleWHERE { ?x b:hasPresentationTitle ?title

FILTER regex(?title, "^Hands") }

Result

"Handson session RDF(S) and SPARQL"

Many possibilities: string matching, value restrictions (greaterThan, etc.), DateTime restrictions, …

OPTIONAL keywordRDF data:@prefix b: <http://www.R4SC.net/building#> .@prefix : <http://www.R4SC.net/today#> .:room_1 b:hasPresentationTitle “RDF(S) and SPARQL" .:room_1 b:hasPeopleInside 28 .:room_2 b:hasPresentationTitle “Handson session RDF(S) and SPARQL" .:room_2 b:hasPeopleInside 23 .

Query@prefix b: <http://www.R4SC.net/building#> .SELECT ?title ?attendeesWHERE { ?x b:hasPresentationTitle ?title . OPTIONAL { ?x b:hasPeopleInside ?attendees. FILTER (?attendees > 25) } }

Result

title attendees

"RDF(S) and SPARQL" 28

"Handson session RDF(S) and SPARQL"

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

LIMIT Keyword

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

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

QueryPREFIX b: <http://www.R4SC.net/building#>SELECT ?nameWHERE { ?x b:hasPersonInside ?name }LIMIT 2

Result

“PieterPauwels"

“RaulGarciaCastro"

ORDER BY

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

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

QueryPREFIX b: <http://www.R4SC.net/building#>SELECT ?nameWHERE { ?x b:hasPersonInside ?name }LIMIT 2 ORDER BY DESC(?name)

Result

“RaulGarciaCastro"

“PieterPauwels"

DISTINCT KeywordRDF data:@prefix b: <http://www.R4SC.net/building#> .@prefix : <http://www.R4SC.net/today#> .:room_1 b:hasPresentation [ b:hasPresentationTitle “RDF(S) and SPARQL" ] .:room_1 b:hasPresentation [ b:hasPresentationTitle “Handson session Generate your RDF”; b:startsAt “14:30:00”^^xsd:time ] .:room_1 b:hasPresentation [ b:hasPresentationTitle “Handson session Generate your RDF”; b:startsAt “17:00:00”^^xsd:time ] .

QueryPREFIX b: < http://www.R4SC.net/building# >SELECT DISTINCT ?titleWHERE { ?x b:hasPresentationTitle ?title}

Result

“RDF(S) and SPARQL"

“Handson session Generate your RDF"

UNION KeywordRDF data:@prefix b: <http://www.R4SC.net/building#> .@prefix : <http://www.R4SC.net/today#> .:room_1 b:hasPresentation [ b:hasPresentationTitle “RDF(S) and SPARQL" ] .:room_1 b:hasPresentation [ b:hasPresentationTitle “Handson session Generate your RDF”; b:startsAt “14:30:00”^^xsd:time ] .:room_1 b:hasPresentation [ b:hasPresentationTitle “Handson session Generate your RDF”; b:startsAt “17:00:00”^^xsd:time ] ._:x1 b:presentation “Linking Data” .

Query@prefix b: <http://www.R4SC.net/building#> .@prefix : <http://www.R4SC.net/today#> .

SELECT DISTINCT ?title_1 ?title_2WHERE { { ?p b:hasPresentationTitle ?title_1 } UNION { ?p1 b:presentation ?title_2 } }

“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:

http://dbpedia.org/sparql

Or even better: host one yourself and make it available

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

Thank you for your attention!

pipauwel.pauwels@ugent.be

Summer School LD4SC 2015 - RDF(S) and SPARQL

Documents

SPARQL-Based Applications for RDF-Encoded Sensor Data

A Transformation Language for RDF based on SPARQL

SUMMER SCHOOL LEX 2014 - RDF + SPARQL querying the web of (lex)data

RDF(S) and SPARQL

Applied Temporal RDF: Efficient Temporal Querying using SPARQL

SPARQL - SPARQL Protocol and RDF Query Languageimss-atenciam/WS/3-sparql.pdf · Interroger les données : SPARQL 2 SPARQL’Protocol’And RDF Query’Language Données liées : 3ème

SPARQL All slides are adapted from the W3C Recommendation SPARQL Query Language for RDF

The RDF* and SPARQL* Approach - Olaf Hartigolafhartig.de/slides/W3CWorkshop2019RDFStarAndSPARQLStar.pdfOlaf Hartig – The RDF/SPARQL Approach to Statement-Level Metadata in RDF

SPARQL Intro: A query language for RDF

Scalable SPARQL Querying of Large RDF Graphs

Linked Data, Rdf & Sparql

Rdf, Sw, Sparql Final

Network Graph Databases, RDF, SPARQL, and SNA

RDF* and SPARQL* - Olaf Hartigolafhartig.de/slides/RDFStarInvitedTalkWSP2018.pdfOlaf Hartig – The RDF/SPARQL Approach to Statement-Level Metadata in RDF 27 Contributions in Detail

BIBFRAME: RDF syntax, BIBFRAME tools and SPARQL

Introduction aux RDF & SPARQL

SPARQL RDF Query Language - Jarrar › ... › WebData › Jarrar.LectureNotes.SPARQL.pdf · 2019-03-12 · Jarrar © 2019 1 SPARQL (RDF Query Language) Mustafa Jarrar: Lecture Notes

An Introduction to the SPARQL RDF Query Languagetw.rpi.edu/2007/11/sparql-intro-gtw.pdf · Overview • Introduction • What is SPARQL • SPARQL Tools • Basics • RDF Nodes and

RDF and SPARQL

Semantic Variation Graphs the case for RDF & SPARQL