Checking a relation in BCNF for MVDs

I give up. I need a guru to answer this, believe me I have spent hours and hours reading books and browsing endless uni websites. Maybe I'm just too dumb. The question seems simple enough.

Let us say there is a relation rel(attr1, attr2, attr3, attr4). It is an all-key relation and for that reason we know it is in BCNF. Now all I have regarding semantics is a textual description of the relation and its attributes (given to me by - yes - my highly estimated lecturer). My question is:

How do I identify MVDs in that relation, without looking at the actual data?

I understand that for a relation with three attributes you would look at

attr1 ->-> attr2 | attr3

and ask yourself: do attr2 and attr3 have a dependency? Then you would look at

attr2 ->-> attr3 | attr1

and ask yourself if attr3 and attr1 have a dependency. Then,

attr3 ->-> attr1 | attr2

and ask about attr1 | attr2. Please correct me if I'm wrong or there's a better way. This might be fine if there are three attributes, but for four it gets cumbersome and for five it's hell.

-seb Received on Mon Jan 06 2003 - 00:29:07 CET