Multi-agent Systems (MAS) are now being considered a promising architectural approach for designing collaborative information systems. In such a perspective, the concept of delegation has often been considered as a key concept for modeling cooperative behavior in MAS. However, despite considerable work on delegation mechanisms in MAS, few research efforts have aimed at truly defining a delegation model for designing MAS. This paper deals with this issue in defining the foundations for a delegation model aimed to help developers during the phase of designing collaborative MAS.