The design and development of open multi-agent systems (MAS) is a key aspect in agent research. We advocate that they can be realised as electronic institutions. In this paper we focus on the execution of electronic institutions by introducing AMELI, an infrastructure that mediates agents? interactions while enforcing institutional rules. An innovative feature of AMELI is that it is of general purpose (it can interpret any institution specification), and therefore it can be regarded as domain-independent. The combination of ISLANDER [5] and AMELI provides full support for the design and development of electronic institutions.