The volatility of business requirements is putting an increasing emphasis on the 
ability for systems to accommodate the changes required by new or different 
organisational needs with a minimum impact on the im-plemented services. 
We propose a discipline for software development centred around the separation 
between what in systems are the basic service-providers (objects) and the 
mechanisms (contracts) through which the be-haviour of these objects is 
coordinated to fulfil business requirements. We show how this separation can be 
sup-ported in platforms for component-based development, making it possible for 
systems to evolve by adding, removing or replacing contracts without having to 
change the rest of the system.