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In definition 3.5 in [3], where we define the class QCQ, for every k 1, we need to add a second requirement for a query to be in the class QCQ, namely that the answer to every query f in the class QCQ is always the union of complete FO types. Previously, we considered that property to be implied by our definition, but it turns out that it is not so. There are total computable queries which for some k 1 preserve realization of FO types for k-tuples, but whose evaluation on some databases defines a relation which has not complete FO types for k-tuples. One example of such queries [1] is the query which defines a total order in the class of Odd Multipedes of Gurevich and Shellah [2]. We give below the correct definition, which should replace definition 3.5 in [3].

Erratum for: A Study of Homogeneity in Relational Databases [Annals of Mathematics and Artificial Intelligence 33(2) (2001) 379–414]