Developing software systems out of components involves defining the overall architecture where such components will cooperate. We argue that major problems with current approaches to component-based software development stem from the fact that architecture is implicit in the components' code. This paper presents a design model for object-oriented systems which makes architecture explicit by letting architecture-transparent components be instantiated and coordinated by separate entities implementing architectural concepts. A brief discussion of the application of the model to the design of a concrete system demonstrates how explicit architecture can enhance the reusability of both components and design elements, and ease the implementation of user-directed dynamic reconfiguration.