In this paper we present ideas and architectural principles upon which we are basing the development of a distributed, open-source infrastructure that, in turn, will support the expression of business models, the dynamic composition of software services, and the optimisation of service chains through automatic self-organising and evolutionary algorithms derived from biology. The target users are small and medium-sized enterprises (SMEs). We call the collection of the infrastructure, the software services, and the SMEs a Digital Business Ecosystem (DBE).