Institute for Informatics
Georg-August-Universität Göttingen

Databases and Information Systems

dbis
Uni Göttingen

Semantic Web
WS 2018/19

Prof. Dr. Wolfgang May,
Lars Runge, M.Sc., Sebastian Schrage, M.Sc.

Date and Time: Tue 14-16, Wed 10-12
Room: IFI 2.101 (North Campus)
Exercises (Übung): integrated into lecture (see announcements on this page)
If (and as long as) non-german-speaking participants attend, the course will be given in english.

Technical Data:6 ECTS credits (Studies in Applied Informatics).

Prerequisites

  • Knowledge in First-Order Logic as taught in "Formale Systeme" is sufficient. Although, prospective participants are recommended to have participated in the lecture Deductive Databases.
  • XML: RDF/XML uses XML as representation, but requires only a little bit of knowledge about XML. A short introduction to XML from that point of view will be given in the lecture.
    XML with DTD, XPath, XQuery, XSLT and XML Schema is the topic of the lecture Semistructured Data and XML (prospectively taking place again in Summer Term 2019).

Note: the module is by default credited as "Core Informatics". It can also be credited as "Applied Informatics". (Decision by the Dean of Studies on 25.10.2006/2.2.2010). In this case, please prepare a personal plan of studies (that e.g. connects it with your application area etc.) and ask for approval by the DoS.

Course Description

  • Short Review: Basic Notions of First-Order Logic
  • RDF: N3 and RDF/XML format, semantics
  • SPARQL: the query language for RDF data
  • RDFS, OWL: having RDF data with additional reasoning
  • Description Logics: the logic underlying OWL
  • Practical experiments with RDF, Jena, Reasoners etc.
  • An experimental Web interface can be found for RDF+OWL and SPARQL here

Dates & Topics

  • First Meeting: Tue 16.10. 14-16: Administrativa, Overview.
    Slides: Introduction and Ontologies
  • Reasoning Motivation: the Einstein/Fish Puzzle ... will (again) be solved declaratively, but totally different than in the "Deductive Databases" lecture.
  • Wed 17.10. Introduction, Web architectures
    Smartboard Notes
  • ... to be extended ...

The SmartBoard Notes are collected here (only relevant ones, so for some dates there are no notes).

The complete slide set can be found here. Please do not print it yet (subject to change); the slides of the SSD&XML lecture can also be found there. Knowledge of XML is only required so far as RDF/XML is (in addition to the N3 format) a possible representation of RDF data. One should be able to "understand" an XML document. XPath/XQuery and XSLT are not required.

Exams

  • Oral exams, several slots to choose between February 4th and April 2019.

Background Literature

P. Hitzler, M. Krötzsch, S. Rudolph, Y. Sure: "Semantic Web - Grundlagen" (in German). Springer eXamen.press, 2008; ISBN 978-3-540-33994-6.
The (german language) book covers nearly exactly the contents of the lecture and also contains an introduction to first-order logic in the appendix.

P. Hitzler, M. Krötzsch, S. Rudolph, Y. Sure: "Foundations of Semantic Web Technologies" (in English). Chapman & Hall/CRC, 2009; ISBN: 9781420090505
The (english language) book covers nearly exactly the contents of the lecture and also contains an introduction to first-order logic in the appendix.

For the part on (first order) logic, and textbook on foundations of logic from the library (e.g. "Logik für Informatiker" (in German) von Uwe Schöning) or the manuscript "Formale Systeme" by Peter H. Schmitt (Uni Karlsruhe) (Kap. 1-5) can be used.

Some Links


Semantic Web Tools and Links

If you experience any problems (forgotten chmod, wrong paths, forgotten updates etc.), please notify us.

Web-wide Services

Professional Tools

Pellet - the OWL Reasoner

  • Pellet Homepage (with Download)
  • Command line usage:
    • set alias (bashrc etc.)
             alias pellet='~dbis/SemWeb-Tools/pellet/pellet.sh'
    • query: pellet query -query-file queryfile inputfile
    • Multiple input files can be used via the JENA-based tool described below.
  • Usage as Web Service (see Slides)
    • For use in the CIP Pool, a Pellet instance running on ap34 can be used at http://ap34.ifi.informatik.uni-goettingen.de/pellet/.
    • If you have an own Pellet on your own computer, start it with ./pellet-dig.sh.
      Pellet usually runs at port 8081. The URL will then be http://localhost:8081.

Jena: RDF and SPARQL

Apache JENA ( https://jena.apache.org/ ) is a free and open source Java framework for building Semantic Web and Linked Data applications.
The course uses a lightweight housemade shell interface to Jena for querying:

  • requires java 1.5
  • set alias (bashrc etc.)
     alias jena='java -jar /afs/informatik.uni-goettingen.de/course/semweb-lecture/JENA-API/semweb.jar'
  • query: (if=input-files, qf=query-file, e.g. in SPARQL)
    jena -q -if inputfiles -qf queryfile
  • general options:
    -il: input language (allows RDF/XML RDF/XML-ABBREV N-TRIPLE N3 TURTLE; N3 is default)
    -if: input files
  • query options:
    -q: query
    -il, -if: as above
    -qf: query-file
  • transform options:
    -t: transform
    -ol: output format (allows RDF/XML RDF/XML-ABBREV N-TRIPLE N3-PLAIN N3-PP N3-TRIPLE N3 TURTLE; N3 is default)
  • export class tree; options:
    -e: export class tree (gives some insight for debugging an ontology ...)
    -il, -if: as above
  • reasoner options (for -q and -e):
    activate reasoning; default: internal reasoner: option -inf (for "inference")
    or use the pellet class that comes with the semweb.jar:
     jena -q -inf -qf query-filename
     jena -q -pellet -qf query-filename

LOD: Accessing RDF Data in the Web

  • rapper: a tool that accesses a Web page in RDF-reading mode to get RDF triples: e.g.
    rapper http://sws.geonames.org/3017382/

Mondial in RDF

The Mondial database in RDF format can be found at http://www.dbis.informatik.uni-goettingen.de/Mondial/#RDF.

Call e.g.

 jena -q -qf mondial-query.sparql
or
 jena -pellet -q -qf mondial-meta-query.sparql

Usage in the CIP Pool

From the CIP Pool computers at the IFI (ground floor or log in from remote), the software and resources are directly accessible:

  • log in from remote to login.stud.informatik.uni-goettingen.de (Linux: ssh, Windows: puTTY)
  • log through to one of the individual computers (e.g. ssh c032)
  • set the alias in your .bashrc file:
     alias jena='java -jar /afs/informatik.uni-goettingen.de/course/semweb-lecture/JENA-API/semweb.jar'
  • The lecture's RDF directory with the n3 files can be found at
     /afs/informatik.uni-goettingen.de/user/d/dbisuser/public_html/teaching/SemWeb/RDF
  • The Mondial files can be found at
     /afs/informatik.uni-goettingen.de/user/d/dbisuser/public_html/Mondial
     /afs/informatik.uni-goettingen.de/user/d/dbisuser/public_html/Mondial/Mondial-RDF