  Data dependencies are integrity constraints that the data of interest must
obey. During the 1980s, Janos Makowsky made a number of contributions to the
study of data dependencies; in particular, he was the first researcher to
characterize data dependencies in terms of their structural properties. The
goal of this article is to first present an overview of Makowsky's work on
characterizing certain classes of data dependencies and then discuss recent
developments concerning characterizations of broader classes of data
dependencies.
