[Haskell-cafe] is anyone familiar with "Comprehending Queries" by Torsten Grust?

Hi all, is anyone here familiar with the paper "Comprehending Queries" by Thorsten Grust? http://kops.ub.uni-konstanz.de/volltexte/1999/312/pdf/312_1.pdf As the paper dates from 1999 I wonder if its content may have been "obsoleted" by later works or if it still is pretty much current. I ask this because I'm still struggling to put my program with lots of queries on a more sound code base. Günther