Composing an application out of independent, reusable pieces has been a key challenge since the early days of software engineering. In this paper we examine some aspects of software architecture. We introduce our COSA+ model built in order to provide some enhancement in the COSA1 one. Our main contributions are the new structure given to an explicit connector, and the conceptual view of the different abstract levels used to define the applications architectures. Profits expected from these improvements are numerous; mainly we can quote the reduction of the production costs and the time to market, simplify the maintenance operations, and foresee supports for the evolution of the software architecture.