sparql tutorial 090313093724 phpapp01

8/12/2019 Sparql Tutorial 090313093724 Phpapp01

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Data Extraction & Exploration

with SPARQL & the Talis

Platform


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Agenda

Tutorial Schema

Graph Patterns

Simple SELECT queries

OPTIONAL patterns

UNION queries

Sorting & Limiting

Filtering & Restrictions

DISTINCT SPARQL Query Forms

Useful Links


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Tutorial Schema

Based on NASA spaceflight data

Available in:

http://api.talis.com/stores/space


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Triple and Graph Patterns

How do we describe the structure of the RDFgraph which we're interested in?


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#An RDF triple in Turtle syntax

foaf:name Sputnik 1.


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#An SPARQL triple pattern, with a single variable

foaf:name ?name.


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#All parts of a triple pattern can be variables

?spacecraftfoaf:name ?name.


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#Matching labels of resources

?subject rdfs:label ?label.


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#Combine triples patterns to create a graph pattern

?subject rdfs:label ?label.?subject rdf:type space:Discipline.


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#SPARQL is based on Turtle, which allows abbreviations#e.g. predicate-object lists:

?subject rdfs:label ?label;

rdf:type space:Discipline.


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#Graph patterns allow us to traverse a graph

?spacecraft foaf:name Sputnik 1.

?launch space:spacecraft ?launch.

?launch space:launched ?launchdate.


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#Graph patterns allow us to traverse a graph

?spacecraft foaf:name Sputnik 1.

?launch space:spacecraft ?launch.

?launch space:launched ?launchdate.


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Structure of a Query

What does a basic SPARQL query look like?


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#Ex. 1#Associate URIs with prefixes

PREFIX space: PREFIX rdf: PREFIX rdfs:

#Example of a SELECT query, retrieving 2 variables#Variables selected MUST be bound in graph pattern

SELECT ?subject ?labelWHERE {

#This is our graph pattern?subject rdfs:label ?label;

rdf:type space:Discipline.}


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#Ex. 2

PREFIX space: PREFIX rdf: PREFIX rdfs:

#Example of a SELECT query, retrieving all variables

SELECT *WHERE {

?subject rdfs:label ?label;rdf:type space:Discipline.

}


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OPTIONAL bindings

How do we allow for missing or unknowninformation?


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#Ex. 3

PREFIX space: PREFIX foaf:

SELECT ?name ?image

WHERE {

#This pattern must be bound?spacecraft foaf:name ?name.

#Anything in this block doesn't have to be boundOPTIONAL {

?spacecraft foaf:depiction ?image.}

}


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UNION queries

How do we allow for alternatives or variations inthe graph?


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#Ex. 4

PREFIX space: PREFIX foaf: PREFIX rdfs:

SELECT ?subject ?displayLabelWHERE {

{?subject foaf:name ?displayLabel.}UNION

{?subject rdfs:label ?displayLabel.}

}
http://xmlns.com/foaf/0.1/http://xmlns.com/foaf/0.1/


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Sorting & Restrictions

How do we apply a sort order to the results?

How can we restrict the number of resultsreturned?


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#Ex.5

#Select the uri and the mass of all the spacecraft


PREFIX rdfs:

SELECT ?spacecraft ?massWHERE {

?spacecraft space:mass ?mass.

}
http://xmlns.com/foaf/0.1/http://xmlns.com/foaf/0.1/


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#Ex. 6

#Select the uri and the mass of all the spacecraft#with highest first

PREFIX space:

PREFIX foaf: PREFIX rdfs:



}#Use an ORDER BY clause to apply a sort. Can be ASC or DESCORDER BY DESC(?mass)
http://xmlns.com/foaf/0.1/http://xmlns.com/foaf/0.1/http://xmlns.com/foaf/0.1/http://xmlns.com/foaf/0.1/


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#Ex. 7

#Select the uri and the mass of the 10 heaviest spacecraft


PREFIX rdfs:



}#Order by weight descendingORDER BY DESC(?mass)#Limit to first ten resultsLIMIT 10


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#Ex. 8

#Select the uri and the mass of the 11-20thmost#heaviest spacecraft

PREFIX space:

PREFIX foaf: PREFIX rdfs:



}ORDER BY DESC(?mass)#Limit to ten resultsLIMIT 10#Apply an offset to get next pageOFFSET 10


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Filtering

How do we restrict results based on aspects of thedata rather than the graph, e.g. string matching?


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#Sample data for Sputnik launch

rdf:type space:Launch;

#Assign a datatype to the literal, to indicate it is#a datespace:launched "1957-10-04"^^xsd:date;

space:spacecraft.


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#Ex. 9

#Select name of spacecraft launched between#1stJan 1969 and 1stJan 1970

PREFIX space:

PREFIX foaf: PREFIX xsd:

SELECT ?nameWHERE {

?launch space:launched ?date;space:spacecraft ?spacecraft.

?spacecraft foaf:name ?name.

FILTER (?date > "1969-01-01"^^xsd:date &&

?date < "1970-01-01"^^xsd:date)

}


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#Ex. 10

#Select spacecraft with a mass of less than 90kg


PREFIX xsd:

SELECT ?spacecraft ?nameWHERE {

?spacecraft foaf:name ?name;space:mass ?mass.

#Note that we have to cast the data to the right type#As it is not declared in the dataFILTER( xsd:double(?mass) < 90.0 )

}


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#Ex. 11

#Select spacecraft with a name like ollo


PREFIX xsd:

SELECT ?nameWHERE {

?spacecraft foaf:name ?name.

FILTER( regex(?name, ollo, i ) )}


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Built-In Filters

Logical: !, &&, ||

Math: +, -, *, /

Comparison: =, !=, >,


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DISTINCT

How do we remove duplicate results?


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#Ex. 12

#Select list of agencies associated with spacecraft


PREFIX xsd:

SELECT DISTINCT ?agencyWHERE {

?spacecraft space:agency ?agency.

}


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SPARQL Query Forms

Does SPARQL do more than just SELECT data?


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ASK

Test whether the graph contains some data ofinterest


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#Ex. 13

#Was there a launch on 16thJuly 1969?

PREFIX space: PREFIX xsd:

ASK WHERE {?launch space:launched "1969-07-16"^^xsd:date.

}


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DESCRIBE

Generate an RDF description of a resource(s)


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#Ex. 14

#Describe launch(es) that occurred on 16thJuly 1969


DESCRIBE ?launch WHERE {?launch space:launched "1969-07-16"^^xsd:date.

}


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#Ex. 15

#Describe spacecraft launched on 16thJuly 1969


DESCRIBE ?spacecraft WHERE {

?launch space:launched "1969-07-16"^^xsd:date.

?spacecraft space:launch ?launch.

}


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CONSTRUCT

Create a custom RDF graph based on query criteria

Can be used to transform RDF data


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#Ex. 16

PREFIX space: PREFIX xsd: PREFIX foaf:

CONSTRUCT {?spacecraft foaf:name ?name;

space:agency ?agency;space:mass ?mass.

}WHERE {


?spacecraft space:launch ?launch;foaf:name ?name;space:agency ?agency;space:mass ?mass.

}


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SELECT

SQL style result set retrieval


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#Ex. 17

PREFIX space: PREFIX xsd: PREFIX foaf:

SELECT ?name ?agency ?massWHERE {


?spacecraft space:launch ?launch;

foaf:name ?name;space:agency ?agency;space:mass ?mass.

}


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Useful Links

SPARQL FAQ http://www.thefigtrees.net/lee/sw/sparql-faq

SPARQL Recipes http://n2.talis.com/wiki/SPARQL_Recipes

SPARQL By Example Tutorial http://www.cambridgesemantics.com/2008/09/sparql-by-example

Twinkle, GUI SPARQL editor http://www.ldodds.com/projects/twinkle

http://code.google.com/p/twinkle-sparql-tools
http://www.thefigtrees.net/lee/sw/sparql-faqhttp://n2.talis.com/wiki/SPARQL_Recipeshttp://www.cambridgesemantics.com/2008/09/sparql-by-examplehttp://www.ldodds.com/projects/twinklehttp://code.google.com/p/twinkle-sparql-toolshttp://code.google.com/p/twinkle-sparql-toolshttp://code.google.com/p/twinkle-sparql-toolshttp://code.google.com/p/twinkle-sparql-toolshttp://code.google.com/p/twinkle-sparql-toolshttp://code.google.com/p/twinkle-sparql-toolshttp://code.google.com/p/twinkle-sparql-toolshttp://www.ldodds.com/projects/twinklehttp://www.ldodds.com/projects/twinklehttp://www.cambridgesemantics.com/2008/09/sparql-by-examplehttp://www.cambridgesemantics.com/2008/09/sparql-by-examplehttp://www.cambridgesemantics.com/2008/09/sparql-by-examplehttp://www.cambridgesemantics.com/2008/09/sparql-by-examplehttp://www.cambridgesemantics.com/2008/09/sparql-by-examplehttp://www.cambridgesemantics.com/2008/09/sparql-by-examplehttp://www.cambridgesemantics.com/2008/09/sparql-by-examplehttp://www.cambridgesemantics.com/2008/09/sparql-by-examplehttp://www.cambridgesemantics.com/2008/09/sparql-by-examplehttp://n2.talis.com/wiki/SPARQL_Recipeshttp://n2.talis.com/wiki/SPARQL_Recipeshttp://n2.talis.com/wiki/SPARQL_Recipeshttp://www.thefigtrees.net/lee/sw/sparql-faqhttp://www.thefigtrees.net/lee/sw/sparql-faqhttp://www.thefigtrees.net/lee/sw/sparql-faq


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