In Leuven, we have studied semantic data-specifications from a categorical perspective. We have studied sketches as a formalism for making semantic data-specifications (somewhat similar to the approach taken by Diskin et al.), and have developed and proved correct a number of interesting algorithms to decide semantical equivalence of such specifications. The following publications describe our work: Frank Piessens, Eric Steegmans. ``Categorical data-specifications'', {\em Theory and Applications of Categories}, Vol. 1, No. 8, 1995, pp. 156--173. Frank Piessens, Eric Steegmans. ``Proving semantical equivalence of data specifications'', accepted for publication in the special issue of {\em The Journal of Pure and Applied Algebra} dedicated to the celebration of Peter Freyd's 60th birthday. Frank Piessens. ``Semantic data specifications: an analysis based on a categorical formalization'', PhD thesis, Dept. of Computer Science, Katholieke Universiteit Leuven, 1996. Frank Piessens.