A design pattern describes a structure of communicating components that solves a commonly occurring design problem. Designing with patterns offers the possibility of raising the abstraction level at which design is performed, with improvements in clarity, understanding, and facility of maintenance of applications. However, in their most common presentation, design patterns are informal pieces of design process, which application is not reflected in the operational system, and the potential advantages of a more principled design are not realized. This work proposes to organize design in such a way that pattern applications remain explicit in the operational systems. A reflective architecture is proposed, where patterns are reified as metalevel constructs.Sociedad Argentina de Informática e Investigación Operativa