Among existing grid middleware approaches, one simple, powerful, and flexible approach consists of using servers available in different administrative domains through the classical client-server or Remote Procedure Call (RPC) paradigm. Network Enabled Servers implement this model also called GridRPC. Clients submit computation requests to a scheduler whose goal is to find a server available on the grid. The aim of this paper is to give an overview of a middleware developed by the GRAAL team called DIET (for Distributed Interactive Engineering Tool-box). DIET is a hierarchical set of components used for the development of applications based on computational servers on the grid.