Lab 4: SPARQL / Blazegraph
- Setting up the Blazegraph graph database. Previously we have only stored our triples in memory, which is not persistent.
- SPARQL queries and updates. We use SPARQL to retrieve of update triples in our databases/graphs of triples
Installing the Blazegraph database on your own computer
Download Blazegraph (blazegraph.jar) from here: https://blazegraph.com/ I recommend placing blazegraph.jar in the same folder of your python project for the labs. Navigate to the folder of blazegraph.jar in your commandline/terminal using cd. (cd C:\Users\Martin\PycharmProjects\info216_labs for me as an example). Now run this command:
java -server -Xmx4g -jar blazegraph.jar
You might have to install java 8 64-bit JDK if you have problems running blazegraph. You can do it from this link: "https://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html" If you get an "Address already in use" error, this is likely because blazegraph has been terminated improperly. Either restart the terminal-session or try to run this command instead:
java -server -Xmx4g -Djetty.port=19999 -jar blazegraph.jar
This changes the port of the blazegraph server.
If it works it should now display an url like: "http://10.0.0.13:9999/blazegraph/". Open this in a browser. You can now run SPARQL queries and updates and load RDF graphs from your file into Blazegraph. In the update tab, load RDF data (select type below) and then paste the contents of your turtle/.txt file to add them all at once to the database. If you have not serialized your graph from lab 2 yet, you can use the triples on the bottom of the page instead. Just copy and paste them into the Update section.
Write the following SPARQL queries:
- 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.
If you have more time
Redo all the above steps, this time writing a Python/RDFlib program. This will be the topic of lab 6. You can look at the python example page to see how to connect to your blazegraph endpoint in Python and how to perform some basic queries.
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 .