Semantic Web Technologies

184.268 - Technologien für das Semantische Web VU, 2008W, 2.0h, TU Vienna

Lecture by Axel Polleres.

Overview

The goal of this lecture with assignments is to provide deeper insights into languages, standards and technologies of the Semantic Web. The special focus here lies on formal Semantics. Further we will show how these standards can be used for inference and querying on the Web, Semantic Web search and Web Services.

Even if the attendance of the course 188.399 "Einführung in Semantic Web VU" is not a prerequisite to attend this course, the present course may be viewed as a continuation where some of the topics presented in 188.399 are presented with from a more theoretical point of view. Prior attendance of 188.399 is thus recommended.

Location and Time

This lecture will be held as a blocked guest lecture between 12 January 2009 and 23 January 2009 at Vienna University of Technology. The first lecture will be held on 12 January 2009, 9am-12pm, in Vortmann Hörsaal. All further organisational details will be announced then. Also check TUWIS for announcements.

Schedule

Blocks:

• 2009-01-12: 09:00 - 12:00, Vortmann Hörsaal: Lecture
• 2009-01-13: 09:00 - 12:00, Seminarraum 184/3: Lecture
• 2009-01-15: 13:00 - 16:00, Zemanek Hörsaal: Lecture
• 2009-01-16: 09:00 - 12:00, Seminarraum 184/2: Lecture
• 2009-01-21: 17:00 - 20:00, Seminarraum 184/3: Q & A
• 2009-01-22: 16:00 - 19:00, Seminarraum 184/2: Lecture

Exam:

• 2009-01-23: Personal appointment with Lecturer! Please register a 15min time slot via TUWIS. The assignments need to be submitted beforehand per e-mail, see below.

Course Material

• 2008-01-12: The Semantic Web - Lecture Overview and Bird’s View on RDF(S), OWL & SPARQL (PDF)
• 2008-01-13: RDF & SPARQL Semantics in detail (PDF)
• 2008-01-15/2008-01-16: Higher Entailment regimes: Semantics of RDF(S) & OWL (PDF)
• Extra slides:
  • SPARQL Tutorial, specially Unit 2a.
  • SAOR - Scalable Authoriatative OWL reasoning
  • Trends & Projects within DERI
• Some test data and queries

Assignments

Assignment 1

• Create your own FOAF file. You can use a generator tool such as FOAF-a-Matic to generate a skeleton.
• Add some custom triples (not auto-generated) to that FOAF-file.
• Link to some of your friends' FOAF files, i.e. other people in the course, by using foaf:knows and rdfs:seeAlso. You can use my foaf-file as an example.
• Go to the SPARQL interface of DBLP at http://dblp.l3s.de/d2r/snorql/. Try to formulate the query of slide 30 of Unit 1

Assignment 2

• Based on your FOAF file, write and evaluate queries that answers the following questions:
  1. First, include a foaf:knows relation to me in your foaf file, along with a rdfs:seeAlso link to my foaf file. (That is only to ensure that some base results will be the same for everybody)
  2. Give me the names of all persons known by your friends. Hint: you might need two queries here, (i) extracting the rdfs:seeAlso links to their FOAF files, (ii) a second query, using the result of the first one as the explicitly given dataset (FROM, FROM NAMED clauses)... unfortunately, nested queries that would do this in one go aren't yet possible in SPARQL, so you need to do this manually, cf. e.g. query6. Give me both queries.
  3. Give me the names of all of my friends and optionally their identifier, if it is a URI (I am not interested in blank nodes, but only in URIs which people gave to themselves)
  4. Give me the names of all of my friends and their home-page (foaf:homepage) or email (foaf:mbox)
  5. Refinement: Give me the names of all of my friends and: if they have a home-page, their home-page, otherwise, if they have an email, their email, otherwise, the address of their foaf FILE.
  6. Write a query on your FOAF file which gives duplicate results.
• Look at the two DBLP and DBPedia example queries at in the testdata folder and run them on the DBLP SPARQL and DBPedia SPARQL interfaces.
1. Find out by SPARQL queries the names and birthplaces of Austrian Scientists mentioned in both DBPedia and DBLP (same name is enough here). You might need again separate queries here. One way to proceed would be to aggregate the relevant data by CONSTRUCT queries first and store those locally, and then ask the final query upon the merge of these newly generated graphs.
2. Free-style: Create some other interesting query using DBPedia or DBLP or another SPARQL endpoint (e.g. LinkedMDB) data using OPTIONAL, UNION and FILTERs

Assignment 3

• Have a look at the axiomatic triples for RDF and RDFS and the informative entailment rules in the appendix of the RDF Specification. Which rules and axiomatic triples are necessary to obtain graph G5 on slide 23 of the Unit 3 slides?
• Write down a the Description Logic axiom (vii) of slide 36 of the Unit 3 as RDF. You can choose Turtle or RDF/XML syntax, as you prefer.

Delivery of solutions

Solutions to all three assignments have to be delivered per e-mail to axel[dot]polleres[at]deri[dot]org by 2009-01-21, 09:00am. Please ensure that all SPARQL queries are submitted in plain text and provide results. Some explaining text might help...