es:ES, T:Type, eq:EqDecider(T), v:T, x:Id, e:{e:E| @loc(e)(x:T)} ,
e':{e':E| eloc e' & (x after e') = v} .
eloc next event in [e;e'] after which x = v & (x after next event in [e;e'] after which x = v) = v & e''[e,next event in [e;e'] after which x = v).((x after e'') = v)