This paper proposes design concepts that allow the conception, underst
anding and development of complex technical structures for open distri
buted systems. The proposed concepts are related to, and partially mot
ivated by, the present work on Open Distributed Processing (ODP). As o
pposed to the current ODP approach, the concepts are aimed at supporti
ng a design trajectory with several, related abstraction levels. Simpl
e examples are used to illustrate the proposed concepts.