i am sorry for not being clear,
i was talking about W-R pair.
in the first schedule mentioned by u, R(A) of S2 is --> reading A from database isnt it?
lets assume it is serializable as S1-->S2
now in S1-->S2, R(A) of S2 is --->reading A from W(A) of S1.
i mean to say there is W-R conflict pair W1(A) - R2(A) in serial schedule S1-->S2, but it is not present in original schedule..