>>Jerry, a question - are you able to identify all the ways your database will be used over the next 3-5 years, and by how many people?
>>
>>(...using a bit of the Socratic method here...odd, since I'm an Aristotelian....but there's a point regarding usability I think you should consider)
>>
>>So do you know the ways your database will be used over time?
>
>!!!!
>
>Would it kill you to say, just once, "Maybe I was mistaken"? Your ego can't possibly be this big.

He is not. I already gave you links that this is a debatable topic and many great authorities in database design share Kevin's approach to not allow NULLs in the Foreign Keys but rather use the predefined value for 'Unknown' and have this as an entry in the primary table.