groups of resident services are controlled by distinct administrations, which manage the infrastructure among local services and commit the communication infrastructure with the rest of the Grid to third parties.
The above point authorizes a hierarchical view of a Grid, as composed of domains interconnected by an inter-domain infrastructure.
However, there is a good reason for not extending the hierarchical decomposition beyond the first level, thus preventing from introducing sub-domains, and further.
Our point is that network service characteristics are difficult to compose: for instance from the fact that l(ab) is the loss rate from a to b, and l(bc) is the loss rate from b to c, one can hardly guess which is the value of l(ac).
In our view, decomposition is useful only if one is able to guess which of the components dominates the others when determining a characteristic of the overall network service.