The analysis of resource allocation related aspects is a precondition for the design and control of Flexible Manufacturing Systems. The formulation of this application-driven problem in terms of Petri nets leads to a class of models, with a specific structure-based characterization, which we explore in this presentation. We will concentrate our efforts on the characterization of the liveness of such models. We will also discuss the structural causes of the non-liveness (deadlock of some manufacturing processes) that will allow to state the foundations to introduce control elements which eliminate all the bad states.