EXERCISES INF3580 SPRING 2010 WEEK 3
A bird.
This document contains exercises made for INF3580. Please send any comments, errors, bug or improvement reports to this exercise set to martige@ifi.uio.no. Feedback is most welcome! Alphabetically thanks to Audun Stolpe, Espen H. Lian, Martin Giese and Rune Dahl for feedback.
The main curriculum for INF3580 spring 2010 is Semantic Web Programming by John Hebeler et al., Wiley Publishing, 2009. They have a website with additional articles and all source code used in the book at http://semwebprogramming.org/. Auxiliary curriculum is the book Foundations of Semantic Web Technologies by Hitzler, Krützsch, Rudolph, CRC Press 2009.
Keep all the work you do for these exercises in a safe
place. Setting up a version control system like cvs, svn or
git for the work you do is smart. You can create a svn repository
on IfI's svn server, see their help section for more
information. There is also a walk-through from old INF3120 on how to
set up a svn repository and connect it to Eclipse, but news is
that you'll need the plug-in subclipse to make it work. Please
contact me if you have any smart tips to share.
1 Jena
Read
- Semantic Web Programming: chapters 3, 2.
This week's exercises will give you the first looks on the Jena API. Use the book to look for examples, but look also at the Jena Framework javadoc, there might be better ways to do things than what is used in the book.
Other resources:
1.1 Creating RDF models with Jena
In this set of exercises we will learn how to create models with Jena. First, we will create the model "by hand", i.e., writing triples like in last week's exercises, then we will do the same using a Jena java program.
1.1.1 Exercise
Slide 7 of the lecture set for the RDF lecture, lecture no. 2, contains a graph which is also found in Figure \ref{fig:graph}. Write an RDF representation of the graph. Add also some of the names of the the resources in the graphs in different languages, e.g., "Cat" spells "Katt" in Norwegian and "Katze" in German.
Use whatever namespace you prefer. The important thing is that you get a good idea of how the file should look like as you will need that in the next exercise.
Graphs are suitable for encoding meaning.
1.1.2 Exercise
Write a java program which creates the same RDF model as you made in the previous exercise and writes the model to a file in the same RDF serialisation language as you used.
1.2 RDF serialisation converter
RDF may be written in different ways, in different serialisations. The common serialisations are RDF/XML, Turtle and N3.
1.2.1 Exercise
Write a Java program which can convert between four
serialisations of RDF: RDF/XML, Turtle, N3 and N-TRIPLE. The
program should take two arguments, input file and output format,
where the file extension of the input file indicate which RDF
syntax the file has and the output format specifies the format to
convert to. The converted output shall be written to standard
output. The common file extensions for RDF/XML, Turtle, N3 and
N-TRIPLE are .rdf, .ttl, .n3 and .nt, respectively.
Running
java your_java_program test.n3 RDF/XML > test.rdf
should convert the file test.n3, which is assumed written in
N3, to RDF/XML format and write to the file test.rdf.
1.2.2 Exercise
Using your RDF syntax converter program, convert the Simpsons RDF graph you wrote in last week's exercise to RDF/XML.
1.2.3 Exercise
Using your RDF syntax converter program, convert the Simpsons RDF graph you wrote in last week's exercise to Turtle.
1.2.4 Exercise
Using your RDF syntax converter program, convert the Simpsons RDF graph you wrote in last week's exercise to N3.
1.2.5 Exercise
Using your RDF syntax converter program, convert the Simpsons RDF graph you wrote in last week's exercise to N-Triples.
1.2.6 Exercise
Explain the differences between the four RDF serialisations. Illustrate your points with examples from the RDF conversions done in these exercises.
1.3 Browsing RDF using Jena
In these exercises we will learn more about Jena by making a program that browses FOAF RDF graphs for friends.
1.3.1 Exercise
Make a java program which reads a FOAF file and lists the names of
all the persons the FOAF person knows and the names of who they
again know, i.e., all friends and the friends of these
friends. The program should not use queries. You can assume that
the name of a person is located in a foaf:name element and the
foaf file of a person is located in a rdfs:seeAlso
element—just like how your own FOAF file should look like if
generated by the FOAF-a-Matic.
1.3.2 Exercise
Run your program on your own FOAF file.
1.4 RDF summary program
When opening OWL ontologies in ontology editors it is common to be presented with some metrics about the ontology, e.g., how many classes and relationships there are and what kinds of axioms are used. In this exercise we will create a similar program, but for RDF graphs.
1.4.1 Exercise
Write a program which reads an RDF file and outputs
- the total number of triples in the file
- the number of distinct subjects, predicates and objects in the graph
-
all types, e.g., all objects in a triple where
rdf:typeis the predicate, and the distinct members of these types
1.4.1.1 Tip
Running your program with the following graph as input
1: @prefix : <http://example.com/> . 2: @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . 3: 4: :m rdf:type :A . 5: :n rdf:type :A . 6: :m :r :o . 7: :q :r :n .
should give a result equivalent of the following:
RDF metrics: summary_test.n3 No. of triples: 4 No. of subject: 3 No. of predicates: 2 No. of objects: 3 TYPES: http://example.com/A http://example.com/n http://example.com/m
1.4.2 Exercise
Use your program to analyse your FOAF file.
1.4.3 Exercise
Use your program to analyse Martin Giese's FOAF file.
1.4.4 Exercise
Use your program to analyse your Simpsons RDF file.
Date: 2010-03-12 15:36:35 CET
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