Problem with data

Dear Experts,

When data is coming from R/3 to BW, what are the places where any changes could be done to the data? I know that in User exit(exit_saplarsap_001), transfer rules mapping, start routine in the update rules.

Are there any other places where any changes are possible? My problem is that the data that was loaded long back(not by me)into ODS donot match with the data that I am extracting now. The R/3 people says nothing has changed since then and ABAPer says no changes in user exit....

Any clue as to what else can have effect?

Thank you.