It does not presuppose any promise on the part of the servient owner.
This seems to be written of a rural servitude (aqua) which was lost by mere disuse, without adverse user by the servient owner.
There must exist a right against the servient owner before there is a right against anybody else.
Then it's a case of dominant and servient tenement—a right of way by user as of right, or by a lost grant.
For such rights might exist to active services which had to be performed by the person who held the servient estate.
Suppose I take this book and change it immediately into a servient human being.