for each-add all objects to the contex
for all-delete all objects from the context
     we use forall for summary purpose and foreach for 
detail purpose

forall : -- while using measure objects will inserted(o/p
context)
foreach:- while using diamension object will inserted (I/p
context)

these above 2 conditions are using in calculation context.

= sum(<revenue> foreach(<year>,<city>)) forall(<year>)