The problem of real size system modelling with basic concurrency models like transition systems, Petri nets or process algebra is that there is no possibility to model easily the system data structures. Algebraic specification is a method well adapted to this last aspect and has been chosen to be mixed with the two major concurrency models which are process algebra and Petri nets. We present in this paper how the 'mixing' is done and what are the consequences concerning concurrency through the case of Lotos and Algebraic nets. Our approach is built on a simple case study which is given in several versions with both formalisms. The first one uses the basic models without algebraic specifications to highlight the data structures modelling problem. The second one is used to present how algebraic specifications are integrated in each concurrency model and the last one focuses on the concurrency aspects. Several propositions are then given in order to enhance the mixing of algebraic specifications and Petri nets or process algebra.

Keywords : Petri net, process algebra, data types, algebraic specification, algebraic net, Lotos.