Komplexpraktikum/Project "Reasoning in Description Logic" in SS 2003
 Initial
meeting
 takes place on April 10 at
11:10 (3. DS) in Room 450. Attending the initial meeting is mandatory for participation in the
praktikum/project.
People who want to participate in the praktikum/project, but have
serious reasons to not attend the initial meeting, please sent an
email until April 8.

Position in curriculum
  Diplomstudiengang Informatik (Diplom
und Bakkalaureatsabschluß), ab 5. Semester
;Wahlpflichtveranstaltung (//4)
 Course of studies Computation Logic; project (12 credits)
 Prerequisites
 for computer scientists: Pflichtvorlesung "Grundlagen der Theoretischen Informatik"
 Organisation
  An initial meeting is held at the beginning of the semester (see
above). In this meeting, a brief presentation of the available topics
will be given (see below). Students then have the opportunity to
choose a topic to work on.
 Each student is assigned a tutor, depending on the topic
chosen. During the semester, there will be regular meetings of the
student and his tutor.
 The results of the praktikum/project will be presented at the end of the
semester in a talk given by the student. Time and date are yet to be
fixed.
 Language
 The language of the initial meeting will be English if attended by CL
students, and German otherwise. Concerning the final presentations,
students may choose to present their work in German or in English.
 Participants Duties
 The participants are expected to read the relevant literature,
and to discuss it with their tutor in order to become acquainted with
the topic chosen. The required implementation work should be carried
out in a structured way, and has to be documented appropriately. If a
topic is shared by two or more participants, acquiring teamworking
skills is another goal of the project. The results of the project have
to be described in a essay (~15 pages) and presented in a 30 minutes talk at
the end of the semester.

Topics
 Some of the topics can be worked on by more than one student
 (1)
The Description Logic EL and recursively defined concepts.
 EL is a Description Logic of rather limited expressive power, which
nevertheless has interesting applications in medicine. Recently, we
have shown that extending EL by recursively defined concepts leaves
the relevant inference problems (like subsumption and instance)
polynomial. The main tool to show this is to translate ELterminologies
into graphs, and show that subsumption/instance corresponds to
the existence of certain simulation relations on graphs. The task
is here to implement and optimize the (known) polynomialtime
algorithms for computing simulation relations, and to test them
on example knowledge bases.
Literature:
 Franz Baader. Terminological Cycles in a Description Logic with
Existential Restrictions. LTCSReport 0202, Chair for Automata
Theory, Institute for Theoretical Computer Science, Dresden
University of Technology, Germany, 2002.
 Monika R. Henzinger, Thomas A. Henzinger
and Peter W. Kopke. Computing Simulations on Finite and
Infinite Graphs. 36th Annual Symposium on Foundations of
Computer Science, IEEE Computer Society Press, Milwaukee,
Wisconsin, 1995, 453462.
 William F. Dowling and Jean Gallier. Lineartime
Algorithms for Testing the Satisfiability of Propositional
Horn Formulae. Journal of Logic Programmming,
1(3):267284, 1984.
Tutor: Franz Baader
 (2)
Implementation of optimized ALCALE Approximations

Approximation is a new reasoning service for description logics that
has recently cought the attention of researchers. The purpose of this
project is to enhance the existing LISP implementation of
approximation for the description logics ALC and ALE by integrating
two optimization techniques: (1) a special treatment of certain
wellbehaved (so called "nice") concepts and (2) implementation of the
socalled "lazy unfolding" of acyclic TBoxes. Both implementations
should then also be evaluated and compared.
Literature:
Tutor: AnniYasmin Turhan.
 (3)
Translating description and modal logics.

Stateoftheart description logic (and modal logic) reasoning systems
such as FaCT and
RACER are
based an tableauxstyle decision procedures. This project is concerned
with another approach to reasoning with such logics, namely the
translation to weak second order logic in one successor (WS1S). Such
translations, which are technically rather straightforward, are of
interest due to the existence of highly optimized WS1S reasoners such
as Mona. The goal of the
project is to write a translator from description (or modal) logic
formulas to WS1S formulas and to couple it with the Mona system.
If time suffices, it would be interesting to investigate the runtime
behaviour of the resulting system.
Literature: The Mona Manual (more to be supplied).
Tutor: Carsten Lutz,
 (4) Design of
an Ontology and description of the experiences made in
the design.

The student may chose any nontrivial area he or she knows
sufficiently well and describe the relevant concepts of this area
using the ontology editors OilEd and Rice . The experiences
made during this design phase should be described thoroughly,
including a comparison of both editors.
Literature: S. Bechhofer,
I. Horrocks, C. Goble, and R. Stevens. OilEd: a reasonable
ontology editor for the semantic web. In Proc. of the Joint German
Austrian Conference on AI, number 2174 in Lecture Notes In
Artificial Intelligence, pages 396408. SpringerVerlag, 2001.
Tutor: Ulrike Sattler,
 (5)
Concept generator for description logics.
 to evaluate the quality of imlemented DL reasoning systems,
it is very useful
to generate a large amount of formulas with certain characteristics.
The goal of this project is to implement a generator for description
logic concepts (i.e., formulas) that takes several parameters,
such as nesting depth and number of atomic concepts, and randomly
generates a set of concepts in accordance with the input parameters.
Literature:
 Ian P. Gent and Toby Walsh. Beyond
NP: The QSAT Phase Transition. Proceedings of AAAI99, 1999.
 I. Horrocks, P. F. PatelSchneider, and R. Sebastiani. An analysis
of empirical testing for modal decision procedures. Logic Journal
of the IGPL, 8(3):293323, 2000.
Tutor: Jan Hladik
 (6)
Implementation of a matching algorithm for the Description Logic ALN.
 A matching problem comprises a concept description and a
socalled concept pattern, i.e., a concept description with
variables. Matching a concept pattern against a concept description
means finding a substitution of the occurring variables by concept
descriptions such that the original concept description is subsumed by
the instantiated concept pattern.
Since matching in the Description Logic ALN is theoretically
wellexamined this topic focusses on the implementation of the
relevant algorithm in LISP and on the evaluation w.r.t. runtime
behaviour.
Literature:
 F. Baader, R. Küsters, A. Borgida, and
D. McGuinness. Matching in Description Logics. Journal of Logic and
Computation, 9(3):411447, 1999.
 S. Brandt. Matching under Side Conditions in Description Logics. Diploma thesis, RWTH Aachen, Germany, 2000.
 Guy L., Jr. Steele. Common Lisp: The Language.
Tutor: Sebastian Brandt
Carsten Lutz