Lab: SPARQL Programming

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Lab 6 - SPARQL PROGRAMMING

Topics

SPARQL programming in python with SPARQLWrapper and Blazegraph, or alternatively RDFlib. These tasks are about programming SPARQL queries and inserts in a python program.

Last week we added triples manually from the web interface.

However, in the majority of cases, we want to program the insertion or updates of triples for our graphs/databases, for instance to handle automatic or scheduled updates.

Tasks

Remember, before you can interact with Blazegraph you have to make sure its running like we did in Lab 4.

  • Make a new blazegraph namespace from the blazegraph web-interface and add all the triples that are on the bottom of the page like we did in Lab 4

Alternatively you can use your own triples if you have them.

The default namespace for blazegraph is "kb". If you want to add other namespaces you can do it from the web-interface of Blazegraph, from the "Namespace" Tab. Remember to click "Use" on the namespace after you have created it.

The different namespaces for blazegraph acts as seperate graphs/databases. This is especially useful if you are using the UiB link to blazegraph: "i2s.uib.no:8888/bigdata/#splash", because with your own namespace, only you can select and update your data.


  • Redo all the SPARQL queries and updates from Lab 4, this time writing a Python program that uses SPARQLWrapper to handle them.
  • SELECT all triples in your graph.
  • SELECT all the interests of Cade.
  • SELECT the city and country of where Emma lives.
  • SELECT only people who are older than 26.
  • SELECT Everyone who graduated with a Bachelor Degree.
  • Use SPARQL Update's DELETE DATA to delete that fact that Cade is interested in Photography. Run your SPARQL query again to check that the graph has changed.
  • Use INSERT DATA to add information about Sergio Pastor, who lives in 4 Carrer del Serpis, 46021 Valencia, Spain. he has a M.Sc. in computer from the University of Valencia from 2008. His areas of expertise include big data, semantic technologies and machine learning.
  • Write a SPARQL DELETE/INSERT update to change the name of "University of Valencia" to "Universidad de Valencia" whereever it occurs.
  • Write a SPARQL DESCRIBE query to get basic information about Sergio.
  • Write a SPARQL CONSTRUCT query that returns that: any city in an address is a cityOf the country of the same address.


With Blazegraph

First, pip install SPARQLWrapper. The most important part is that we need to import a SPARQLWrapper in order to connect to the SPARQL endpoint of Blazegraph.

When it comes to how to do some queries and updates I recommend scrolling down on this page for help: https://github.com/RDFLib/sparqlwrapper. There are also some examples on our example page.

Remember, before you can program with Blazegraph you have to make sure its running like we did in Lab 4. Make sure that the URL you use with SPARQLWrapper has the same address and port as the one you get from running it. Now you will be able to program queries and updates.

# How to establish connection to Blazegraph endpoint. Also a quick select example.

from SPARQLWrapper import SPARQLWrapper, JSON

namespace = "kb"
sparql = SPARQLWrapper("http://localhost:9999/blazegraph/namespace/"+ namespace + "/sparql")

sparql.setQuery("""
    PREFIX ex: <http://example.org/>
    SELECT * WHERE {
    ex:Cade ex:interest ?interest.
    }
""")
sparql.setReturnFormat(JSON)

results = sparql.query().convert()

for result in results["results"]["bindings"]:
    print(result["interest"]["value"])

The different types of queries requires different return formats:

  • SELECT and ASK: a SPARQL Results Document in XML, JSON, or CSV/TSV format.
  • DESCRIBE and CONSTRUCT: an RDF graph serialized, for example, in the TURTLE or RDF/XML syntax, or an equivalent RDF graph serialization.

Remember to make sure that you can see the changes that take place after your inserts.


Without Blazegraph

If you have not been able to run Blazegraph on your own computer yet, you can use the UiB blazegraph service: i2s.uib.no:8888/bigdata/#splash. Remember to create your own namespace like said above in the web-interface.

Alternatively, you can instead program SPARQL queries directly with RDFlib.

For help, look at the link below:

Querying with Sparql


Useful Readings

SPARQL Queries you can use for tasks

# SPARQL Queries

prefix ex: <http://example.org/>

# SELECT Every triple
SELECT * WHERE {?s ?p ?o}

# Select the interests of Cade
SELECT ?interest WHERE {ex:Cade ex:interest ?interest}

# SELECT only people who are older than 26
SELECT ?person ?age WHERE {?person ex:age ?age. FILTER(?age > 26)}

# SELECT The City and country of Cade
SELECT ?country ?city WHERE {ex:Cade ex:address ?address. ?address ex:country ?country. ?address ex:city ?city.}

# SELECT Everyone who graduated with a Bachelor Degree.
SELECT ?person ?level WHERE {?person ex:degree ?degree. ?degree ex:degreeLevel ?level. FILTER(?level="Bachelor")}

# DELETE Photography
PREFIX ex: <http://example.org/>
DELETE DATA

{
 ex:Cade ex:interest ex:Photography.
}


# INSERT Sergio

PREFIX ex: <http://example.org/>

INSERT DATA
{
 ex:Sergio ex:address ex:SergioAddress.
 ex:SergioAddress ex:city ex:Valencia.
 ex:SergioAddress ex:street "4 Carrer del Serpis".
 ex:SergioAddress ex:postalCode "46021".
 ex:SergioAddress ex:country ex:Spain.
 ex:Sergio ex:address ex:SergioDegree.
 ex:SergioDegree ex:degreeLevel "Master".
 ex:SergioDegree ex:degreeField ex:Computer_Science.
 ex:SergioDegree ex:degreeYear "2008".
 ex:SergioDegree ex:degreeSource ex:University_of_Valencia.
 ex:Sergio ex:expertise ex:Big_Data.
 ex:Sergio ex:expertise ex:Semantic_Technologies.
 ex:Sergio ex:expertise ex:Machine_Learning.
}


# DELETE Photography
PREFIX ex: <http://example.org/>
DELETE DATA

{
 ex:Cade ex:interest ex:Photography.
}

# DELETE/INSERT University

prefix ex: <http://example.org/>

DELETE {
  ?s ?p ex:University_of_Valencia.
}
INSERT {?s ?p ex:Universidad_de_Valencia.}

WHERE {
?s ?p ex:University_of_Valencia.}


# Construct

prefix ex: <http://example.org/>

CONSTRUCT {?city ex:cityOf ?country}
WHERE {?address ex:city ?city. ?address ex:country ?country}


Triples that you can base your queries on: (turtle format)

@prefix ex: <http://example.org/> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix xml: <http://www.w3.org/XML/1998/namespace> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

ex:Cade a foaf:Person ;
    ex:address [ a ex:Address ;
            ex:city ex:Berkeley ;
            ex:country ex:USA ;
            ex:postalCode "94709"^^xsd:string ;
            ex:state ex:California ;
            ex:street "1516_Henry_Street"^^xsd:string ] ;
    ex:age 27 ;
    ex:characteristic ex:Kind ;
    ex:degree [ ex:degreeField ex:Biology ;
            ex:degreeLevel "Bachelor"^^xsd:string ;
            ex:degreeSource ex:University_of_California ;
            ex:year "2011-01-01"^^xsd:gYear ] ;
    ex:interest ex:Bird,
        ex:Ecology,
        ex:Environmentalism,
        ex:Photography,
        ex:Travelling ;
    ex:married ex:Mary ;
    ex:meeting ex:Meeting1 ;
    ex:visit ex:Canada,
        ex:France,
        ex:Germany ;
    foaf:knows ex:Emma ;
    foaf:name "Cade_Tracey"^^xsd:string .

ex:Mary a ex:Student,
        foaf:Person ;
    ex:age 26 ;
    ex:characteristic ex:Kind ;
    ex:interest ex:Biology,
        ex:Chocolate,
        ex:Hiking .

ex:Emma a foaf:Person ;
    ex:address [ a ex:Address ;
            ex:city ex:Valencia ;
            ex:country ex:Spain ;
            ex:postalCode "46020"^^xsd:string ;
            ex:street "Carrer_de_la Guardia_Civil_20"^^xsd:string ] ;
    ex:age 26 ;
    ex:degree [ ex:degreeField ex:Chemistry ;
            ex:degreeLevel "Master"^^xsd:string ;
            ex:degreeSource ex:University_of_Valencia ;
            ex:year "2015-01-01"^^xsd:gYear ] ;
    ex:expertise ex:Air_Pollution,
        ex:Toxic_Waste,
        ex:Waste_Management ;
    ex:interest ex:Bike_Riding,
        ex:Music,
        ex:Travelling ;
    ex:meeting ex:Meeting1 ;
    ex:visit ( ex:Portugal ex:Italy ex:France ex:Germany ex:Denmark ex:Sweden ) ;
    foaf:name "Emma_Dominguez"^^xsd:string .

ex:Meeting1 a ex:Meeting ;
    ex:date "August, 2014"^^xsd:string ;
    ex:involved ex:Cade,
        ex:Emma ;
    ex:location ex:Paris .

ex:Paris a ex:City ;
    ex:capitalOf ex:France ;
    ex:locatedIn ex:France .

ex:France ex:capital ex:Paris .