In this paper, the authors describe a custom relational algebra query software environment that enables database instructors to teach relational algebra programming. Instead of defining query ...

(iii) Suppose the relation Likes contains all information about all customers. In other words, if the pair (cname,pizza) is not in the relation Likes, it means that the customer cname dislikes the ...

Abstract: Extensive work has recently been done on the evaluation of positive queries on probabilistic databases. The case of queries with negation has notoriously been left out, since it raises ...

(a) Consider again Question 3 in Tutorial 1 (Challenge) to find the restaurants that sell all the pizzas that Maggie likes and don’t sell any pizza that Ralph likes. Write a relational algebra ...