During the 1970's a theory of data ases began to evolve pro- viding a foundation for some existing tools and techniques. The significance of this theory is beginning to have an impact particu- larly with respect to the design and implementation of the relational model of data bases. To further the state of the art in the theory of data bases, a workshop was held in TOulouse, France on December 12-14, 1979. The workshop was a sequel to one held two years previously and entitled, "Logic and Data Base Workshop". As with the earlier work- shop, the meetings were conducted at the centre d'Etudes et de Recherches de l'Ecole Nationale Superieure de l'Aeronautique et de l'Espace de Toulouse (C.E.R.T). We are pleased to acknowledge the financial support received from the Direction des Recherches, Etudes et Techniques d'Armement (D.R.E.T.), and from C.E.R.T. that made the workshop possible.