Just open pretty old Fox system. Obviously, it was written by some stupid guys (not one) who used to set relation in wrong way like:
SELECT child
SET RELATION TO .... INTO parent
System works so far, and I see that all data retrieval bases on SELECT-SQL, so RELATIONs actually are not in use. But I am really afraid to remove/change them once and forever. My question is: could wrongly set, but not used relations corrupt data, offend data integrity or something else?