Saarland University Database Group
Lehrstuhl für Informationssysteme
Prof. Christoph Koch
Universität des Saarlandes
Fachrichtung 6.2 - Informatik
D-66041 Saarbrücken, Germany
Building 36.1, 2nd floor
Talk Announcement
On the Minimization of XML Schemas and Tree Automata for Unranked Trees
Speaker: Wim Martens, University of Hasselt, Belgium
Abstract:
Automata for unranked trees form a foundation for XML schemas, querying, and pattern languages. We study the problem of efficiently minimizing such
automata. We start with the unranked tree automata (UTAs) that are standard in database theory, assuming bottom-up determinism and that horizontal
recursion is represented by deterministic finite automata. We show that minimal UTAs in that class are not unique and that minimization is NP-hard. We
then study more recent automata classes that do allow for polynomial time minimization. Among those, we show that bottom-up deterministic stepwise
tree automata yield the most succinct representations. Further, we investigate a notion of top-down determinism that captures a strict superset of the
expressive power of XML Schema. In this respect, we show that top-down deterministic schemas can be minimized in polynomial time, and that minimal
schemas are unique up to isomorphism.
Time and location:
In Informatik-Kolloquium,
Saarland University.
Oct 10, 2005, 4 p.m. in room 4.07 (building 36.1).
Additional Material: Slides
from the talk.
Last updated Oct 19, 2005.