In this paper we propose a number of extensions for object-oriented models in order to describe dynamic aspects of applications. These extensions enable the specification of objects that modify their behavior dynamically and the control of the dynamic evolution of objects by means of constraints expressed in the language of propositional temporal logic. We shall point out what differentiates our proposal from existing models and give examples to illustrate our arguments. We aIso present an algorithm for verifying consistency of specifications and which is suitable for an eventual implementation of our extensions.