how to specify that in SERVICE VAR how we query all possible sparql endpoints

Hello all,

I've been working in dividing the Fed extension semantics section in two,
one for SERVICE and another one for SERVICE VAR. I just added new semantics
definition for SERVICE VAR, but now, in that part I do not know how to
specify that when doing SERVICE ?X, ?X may be still not bounded and a query
to all possible values may happen. Any idea?

thanks a lot :)

Carlos

PS the document is still in an early stage, which I hope I will finish today
and tomorrow will be ready with all Greg's comments solved