  Distribution system and market operators will need or be required to monitor
closely distribution systems, due to the presence of multiple actors, such as
generating and storage units, as also active loads. The reason for this is the
effect of these latter actors to system operation as also to ensure they follow
their commitments in the deregulated market frameworks. This paper discusses
why the traditional approach to state estimation as this has been developed for
transmission systems cannot be extended to distribution systems. Some
preliminary proposals are made, and a high-level architecture is presented as
part of an on-going research work on the matter.
