This is a position paper reporting the motivations, the starting point and the guidelines that characterise the MERCURIO project proposal, submitted to MIUR PRIN 2009. The aim is to develop formal models of interactions and of the related support infrastructures, that overcome the limits of the current approaches by explicitly representing not only the agents but also the computational environment in terms of rules, conventions, resources, tools, and services that are functional to the coordination and cooperation of the agents. The models will enable the verification of interaction properties of MAS from the global point of view of the system as well as from the point of view of the single agents, due to the introduction a novel social semantic of interaction based on commitments and on an explicit account of the regulative rules.