Lab: RDF programming with RDFlib

Topics

• Basic RDF graph programming with RDFlib.
• Simple reading/writing from/to file.
• Simple looping through graph

Useful Links

rdflib documentation:

• Creating Triples
• Navigating Graphs
• Parsing

Useful rdflib classes/interfaces and methods

from rdflib import Graph, Namespace, URIRef, BNode, Literal

from rdflib.namespace import RDF, FOAF, XSD

from rdflib.collection import Collection

Methods: Graph - add(), remove(), triples(), serialize(), parse(), bind()

Tasks

Consider the following situation: "Cade lives in 1516 Henry Street, Berkeley, California 94709, USA. He has a B.Sc. in biology from the University of California, Berkeley from 2011. His interests include birds, ecology, the environment, photography and travelling. He has visited Canada and France. Emma Dominguez lives in Carrer de la Guardia Civil 20, 46020 Valencia, Spain. She has a M.Sc. in chemistry from the University of Valencia from 2015. Her areas of expertise include waste management, toxic waste, air pollution. Her interests include bike riding, music and travelling. She has visited Portugal, Italy, France, Germany, Denmark and Sweden. Cade knows Emma. They met in Paris in August 2014."

Create a graph in RDFlib with triples corresponding to the text above. Build on the graph from lab 1. Use your own URIs when you need to (like "http://example.org/"), but try to use terms from vocabularies such as FOAF, RDF, XSD, and others.

Write out your graph to the console. This seems to be the cleanest way of printing the graph to me: print(g.serialize(format="turtle")) But try all the following formats: "turtle", "n3", "nt", "json-ld", "xml". How do they differ? What is the default?

Write your graph to a file. To do this, you can simply use the location parameter e.g: g.serialize(destination="triples.txt", format="turtle").

Look at the file and edit it so that Cade has also visited Germany and so that Emma is 26 years old.

Create a new program that reads your graph in again from the file and writes it to the console. e.g g.parse(location="triples.txt", format="turtle") Check that your new data is there!

Continuing with either your first or second program, write a loop that goes through all the triples in the graph and prints them to the console.

Change the loop so that (a) it only loops through triples about Emma (b) it only loops through triples involving the names of people.

Remove all triples about Mary using graph.remove(). (triples of Mary are from lab 1)

If you have more time...

Task: Write a method (function) that starts with Donald Trump prints out a graph depth-first to show how the other graph nodes are connected to him. For example, the output could be:

ex:Donald_Trump
    ^ex:campaignManager ex:Paul_Manafort
        ex:convictedFor ex:BankAndTaxFraud
        ...
    ^ex:attorneyFor ex:Michael_Cohen
        ex:pleadedGuilty ex:LyingToCongress

Here, the ^-sign is used to indicate the reverse of a property. Note: because you must follow triples in both subject-to-predicate and predicate-to-subject direction, you must keep a list of already visited nodes, and never return to a previously visited one.

Lecture Notes