Institute for Informatics
Georg-August-Universität Göttingen

Databases and Information Systems

dbis
Uni Göttingen

Semantic Web
Winter 2012/13

Prof. Dr. Wolfgang May
Assistance: Daniel Schubert

Date and Time: Wednesday 10-12 ct, Friday 14-16 ct.
Exercises (Übung): integrated into lecture
Room: IFI 2.101 (North Campus)

Technical Data:
3+1 SWS, 6 ECTS credits (Studies in Applied Informatics),

Prerequisites

  • Knowledge in First-Order Logic as taught in "Formale Systeme" is sufficient. Although, prospective participants are strongly recommended to have participated in the lecture Database Theory.
  • 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 2013).

Note: the module can 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
  • RDFS, OWL: having RDF data with additional reasoning
  • Description Logics: the logic underlying OWL
  • Practical experiments with RDF, Jena, Reasoners etc.

Dates & Topics

  • 24.10.: Administrativa, Overview.
    Smartboard Notes (connections with other DBIS lectures, SW buzzword overview)
  • 25.10.: Ontologies
    Slides: Introduction and Ontologies [1-on-1, 2-on-1]
  • 31.10.: Ontologies (cont'd)
    Smartboard Notes (Data Models etc.)
  • 1.11.: Ontologies (cont'd)
    Smartboard Notes (formal specification)
  • 7.11. Introduction to first-order logic and basic notions of model theory.
    Slides: Introduction to Logics [1-on-1, 2-on-1] ... kurz, weil aus DBT bekannt.
  • Reasoning Motivation: the Einstein/Fish Puzzle ... auch das wird wieder deklarativ gelöst, nur gaaaanz anders als in DBT.
  • Kommentar: 5.11.2012: Notenliste DBT an PA übermittelt. Müsste also bald in FlexNever erscheinen. Die Scheine können ebenfalls bei Frau Jachinke abgeholt werden.
  • 7.11. Recall: first-order logic and basic notions of model theory (cont'd).
    Smartboard Notes (mapping ER to relational vs. vertically partitioned; sketches)
  • 14.11.: RDF
    Slides: RDF [1-on-1, 2-on-1]
    Note: all example files are accessible in the RDF subdirectory of this Web page.
    Smartboard Notes (several sketches ...)
  • 15.11. keine Veranstaltung (das können wir uns leisten, letztes Mal fiel viel mehr aus).
  • 21.11.: RDF (Cont'd)
    Note: Slides for "Logic" (shortened, final) and "RDF" have been updated.
    Smartboard Notes (several sketches ...)
  • 22.11.: RDF, SPARQL (Cont'd)
  • 28.11.: RDF, SPARQL (Cont'd)
    Smartboard Notes (several sketches ...)
    Exercise Sheet 1
  • 28.11. evening: Slides RDF [1-on-1, 2-on-1] updated
  • 29.11.: Discussion Exercise Sheet 1
    Smartboard Notes (several sketches ...)
  • Mi 5.12.: lecture (as usual, 10:15-11:45) RDF cont'd [discuss rescheduling of thursday slot]
    Smartboard Notes (several sketches ...)
    Solution (note: the exercises have been restructured and some more ... for next year)
  • Fr 7.12.: RDFS
    Slides: RDFS [1-on-1, 2-on-1]
    Smartboard Notes (several sketches ...)
  • 12.12.: RDFS (Cont'd), RDF/XML - shortly the main ideas. RDF/XML ist nothing conceptually new, but (if one knows XML well) mainly craft, like using URIs, and element names and namespaces, and xml:base.
    Slides: RDF/XML [1-on-1, 2-on-1]
    Smartboard Notes (several sketches ...)
  • 14.12.: RDF/XML (Cont'd), Description Logics
    Slides: DL [1-on-1, 2-on-1]
    Smartboard Notes (several sketches ...)
  • 19./20.12.2012: no lecture
  • Note: Slides 143-146 have been added on SPARQL 1.1 syntax (8.1.2013)
  • 9./11.1.2013: OWL 1.0
    Slides: OWL [1-on-1, 2-on-1]
    Smartboard Notes (11.1.) (several sketches ...)
  • 16./18.1.2013: OWL 1.0 (Cont'd)
    Smartboard Notes (18.1.) (several sketches ...)
  • 23.1.2013: OWL 1.0 (Cont'd)
    Smartboard Notes (23.1.) (several sketches ...)
  • 25.1.2013: und die restlichen Folien: OWL 2.0
    Slides: OWL 2.0 [1-on-1, 2-on-1]
  • Exercise: the Einstein/Fish Puzzle.
  • 30.1./1.2.: OWL 2.0 (Cont'd)
    Smartboard Notes (30.1.), Smartboard Notes (1.2.) (several sketches ...)
  • Discussion of the win-move, "Maria", and uncle/role-chain exercises.
  • 6./8.2.: Tableaux, Rules, Fish Puzzle Smartboard Notes (6.2.), Smartboard Notes (8.2.).
  • in der letzten Vorlesung wurde (kurz) die Lösung des Fishpuzzle besprochen:
    • fishpuzzleLong.n3 ist eine ausführliche Spezifikation:
      Teil 1: Spezifikation der Reihe von 5 Häusern.
      Teil 2: Spezifikation der Eigenschaften.
      Teil 3: Spezifikation der Constraints.
    • fishpuzzleLong.sparql ist die Anfrage dazu.
    • fishpuzzleShort.n3
      Teil 1: Spezifikation der Reihe von 5 Häusern wie oben.
      Teil 2: Trick: Codierung der Eigenschaften. Anstatt jedem Haus ein Farbe und einen Bewohner, und diesem eine Zigarettenmarke, ein Getränk und ein Tier über explizite Kanten zuzuordnen, "setzt man diese gleich" und bildet Äquivalenzklassen.
      Teil 3: Spezifikation der Constraints. Einfacher als vorher, da man nur die Äquivalenzklassen betrachtet.
    • fishpuzzleShort.sparql ist die Anfrage dazu.

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.

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.

Exams

  • Oral exams, date+time flexible between February 11 and April 12 (first week of summer lecture); probably not second half of March.
  • Exam procedure: about 30-40 minutes. Candidates start with talking about a topic of their choice (5-10 minutes), then questions+answers, including sketched on paper develops dynamically.
  • Registration via FlexNever: every participant must be registered in the system.
    • "Standard" regulation for oral exams that do not happen all on the same day:
      • Exams in Module X between T1 and T2
      • oral exams: students may deregister until the very last day before T1 (correct would be: very last day before their individual exam).
      • only registered candidates are allowed to be examined.
    • Practical Algorithm:
      • Exams between 11.2.-12.4.
      • Registration until 12.4.
      • Deregistration: until 10.2.
      • D.h., during 11.2.-12.4. it is possible to register, but not to deregister.
      • make appointment with me via e-mail (individual appointments cannot be administered at all via FlexNever)
      • register in the system at latest in the morning of the individual exam (then I can check the registration just before the exam).
      • For checking if your personal registration works, register today, and just deregister shortly later.
    • Module number M.Inf.1142.Mp or M.Inf.142.6C (6 CP).

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

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

The course uses a lightweight housemade shell interface to Jena for querying, located at /afs/informatik.uni-goettingen.de/course/semweb-lecture/JENA-API/semweb.jar

  • 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 -r pellet -qf query-filename
    or short
     jena -q -pellet -qf query-filename
    or use an external reasoner: options -inf -r reasoner-url
    e.g. use the Pellet instance running at ap34 as external reasoner from the CIP Pool:
     jena -q -qf query-filename -inf -r http://ap34.ifi.informatik.uni-goettingen.de/pellet/ 
  • use of a rule file with the Jena Rule Reasoner (not combined with the Pellet OWL Reasoner):
         -rf  file containing the rules for the ruleengine

IsaViz: RDF Graph Visualizer

  • IsaViz is used for visualization of RDF-Graphs, installed locally at: /afs/informatik.uni-goettingen.de/course/semweb-lecture/tools/IsaViz/
  • You can either change into that directory and start the program with the command ./run.sh or by using an alias pointing to that script. In the latter case you will need to copy the configuration file isaviz.cfg into your home directory.
  • If you want to run the application on your own computer, you will have to install graphviz as well, either from its Web page or from the appropriate package provided by your distribution (e.g. debian-package graphviz).

Mondial in RDF

http://www.dbis.informatik.uni-goettingen.de/Mondial/#RDF

Call e.g.

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