In this paper we describe a conceptual model which is purposed for the modelling of the control integration aspect of Software Engineering Environments (SEE). We present a graphical notation for this model under the notion of Tool/Document (T/D) model which is based on predicate/transition Petri nets. It has therefore a formal semantics and can be further processed for reasons of validation and implementation. Moreover we embed this model methodically in the development process of SEEs by taking also into account that such systems must be integrated into companies with different structures, processes, and requirements. This is one of the reasons why we think that it is necessary to first model and validate relevant parts of a SEE in order to minimize costs and risks. As a case study for this model we use parts of the object-oriented CASE tool OBLOG-CASE.