OSMOSIS [Bézivin1995] is a research platform intended to investigate the various forms of products and processes in object-oriented software production. The kernel of this system is made of a minimal representation support called sNets, a typed, reflective and modular kind of semantic network. Each model represented in this network is composed of a number of typed entities (nodes) and relations between these entities (links) i.e. each model is a partition in the sNet called a universe. For each such universe, there is another one called its semantic universe defining the corresponding ontology. In short, an ontology specifies the concepts that may be used and the possible relations between these concepts. Our kernel sNet notation may be qualified of a NOON (Non Object-Oriented Notation) because the concepts of class or object are not built-in in our system. One reason for this choice is to cater to many different semantics for classes, objects and instanceOf/isA relations. We stress here some of the consequences of these choices on the architecture of meta-levels and show the strong relation between this architecture and the precise definition of the instanciation relations in different contexts. Our illustration will be based on CDIF [Ernst1997].