Can we use the extended relational algebra, or just the core?
Answer: You may use the extended algebra unless we say otherwise.
Should we assume relational algebra is an algebra of sets or bags?
Answer: Sets, unless we ask for the bag version explicitly.
In problem 6, do we need to justify our answer?
Answer: I forgot to require an explanation, but I think people should give a brief explanation. It's not hard, once you see what the right answer is.
In problem 2(b), does ``any'' really mean ``exists''?
Answer: No; the intention was coloquial. We're really asking if the employee makes more than every manager.
How should we express our relational-algebra expressions?
Answer: Any of the notations we used in class is OK: trees, plain old expressions, or the linear sequence of assignments.