what's the aim?

i was hoping for a definition or at least description of what a grid might be
in this context.  we've got a big book of grids in the office, but there must
many different things described in it all called `grid'. (although in several
cases it seems to be the same as what they were working on before grids
became fashionable but with ``... for the grid'' or ``grid-oriented'' added somewhere
presumably to get the funding).

what functionality, scale, etc. have you got in mind?  what's this `grid' supposed
to do?  i understand other requirements here, such as `decentralised' for instance,
but even then there are different strategies depending on the scale desired.