I've got this functional dependency, Department -> HOD(Head-Of-Department). But what do I do in case of change in the HOD of a department? Should I consider this dependency at all since for the same dept. in 2 tuples, diff. values of HOD would exist? Or is it better that the old HOD is overwritten by the new HOD? Same goes for class teacher. But this method reduces the usability of the software since we can't view which HOD a particular batch was under.
If we don't consider the dependency, a very large no. of tuples would contain same value of HOD. I may be wrong. If you think I'm confused, do help me out.
In OODBMS, we could create something like a linked list but still we cannot store which HOD was there for which batch? In RDBMS even this is not possible as far as I know. Or is it? If yes, how? Else, what do I do?