Sustainability is explored as a social construct. It is not just a development goal in itself, but a “transformation process” initially exogenous to the sector with an early economic drive. The notion is linked above all to the future and the differentiated perception of it. Social interactions build areas of knowledge which are historically and socially specific, then later institutionalised and legitimised. Sustainability can be defined as a shared community of practice with an increasing quest for checklists and nevertheless a challenge to achieve and assess.