Tool support helps developers of information systems to considerably increase the accuracy and quality of its models. The use of formal languages in the conceptual modelling process allows the construction of powerful validation tools by executing the model. Executing a model is a very difficult task, when not impossible, due to the high level of abstraction in which it is described. In this paper we analyse some aspects to be taken into account when executing models specified with the formal object-oriented language \sc Troll.