On the Translatability of View Updates

We revisit the view update problem and the abstract functional framework by Bancilhon and Spyratos in a setting where views and updates are exactly given by functions that are expressible in first-order logic. We give a characterisation of views and their inverses based on the notion of definability, and we introduce a general method for checking whether a view update can be uniquely translated as an update of the underlying database under the constant complement principle. We study the setting consisting of a single database relation and two views defined by projections and we compare our general criterium for translatability with the known results for the case in which the constraints on the database are given by functional dependencies. We extend the setting to any number of projective views, rather than just two, and full dependencies (that is, egd’s and full tgd’s) as database constraints, rather than functional dependencies only.