> It is also a bad idea to use proprietary BIT data types to fake
> assembly language style programming. SQL is a predicate language;
> that is, we discover a fact with a predicate rather than set a flag.

What if the fact IS a flag, and is not based on other data in your database?
e.g. did the patient visit Congo anytime between 1978 and 1989? Instead of
a "flag" saying yes or no, would you rather store each patient's entire
travel itineraries for the period in question? What do you when that is not
available, but the patient does know that he/she was there during that time
period?

You can't answer 8 billion different design questions with your four
standards-based rules. Real world design and development dictates a little
more flexibility than that.