Fall Seminar on Data and Knowledge Integration: this week

[Chitta Baral <chitta@asu.edu>]

The sixth talk of the seminar series
  will be this Friday.
 
   Date: 10/11/02 (Friday)
   Time: 11:00 -- 12:15 PM
   Place: GWC 487
  
  Speaker: K. Selcuk Candan

He plans to present the paper
"On the Expressive Power of Data Integration Systems" by
Cali, Calvanese, De Giacomo, and Lenzerini.

This paper is about to be presented at 21st Int. Conf. on Conceptual 
Modeling (ER 2002), and here is its abstract (taken directly from the
paper)

"There are basically two approaches for designing a data integration
system. In the global-as-view (GAV) approach, one maps the concepts in
the global schema to views over the sources, whereas in the
local-as-view (LAV) approach, one maps the sources into views over the
global schema. The goal of this paper is to relate the two approaches
with respect to their expressive power. The analysis is carried out in a
relational database setting, where both the queries on the global
schema, and the views in the mapping are conjunctive queries. We
introduce the notion of query-preserving transformation, and
query-reducibility between data integration systems, and we show that,
when no integrity constraints are allowed in global schema, the LAV and
the GAV approaches are incomparable. We then consider the addition of
integrity constraints in the global schema, and present techniques for
query-preserving transformations in both directions. Finally, we show
that our results imply that w!
e can always transform any system following the GLAV approach (a
generalization of both LAV and GAV) into a query-preserving GAV system."

The paper is available at
http://www.dis.uniroma1.it/~calvanes/papers-html/ER-2002.html


 
-- 
 Chitta Baral
 Dept. of Computer Sc. and Engg.,
 Arizona State University, Tempe, AZ 85287, USA.
 chitta@asu.edu, http://www.public.asu.edu/~cbaral/
 Ph: 480-727-6047, Fax: 480-965-2751