In this paper we address the problem of modelling and using overlap relationships between process workproducts. In fact, in the current MDE context, the nature of software processes has drastically changed; they involve workproducts which are essentially large-sized models with lots of relationships of different kinds. Particularly, we have focused on the overlap relationship which consists in sharing model elements between process workproducts. First, we show that if such relationship is completely specified during process modelling, then process engines are able to use it to ensure a more optimized workproducts management which is not supported by current process management approaches. Then we present our software process modelling and execution approach and describe the prototype of PSEE we have developed to show its feasibility.