Domain and Tuple relational calculus

Question

Is there a "real" difference between the above two? Other than the tiniest minute difference between their syntax?

Answer 1

From what I recall they're equally expressive - that is, anything that can be expressed using domain relational algebra can also be expressed using tuple relational calculus. Some people find DRA easier to interpret...

Answer 2

Domain calculus differs from tuple calculus in the type of variables used in formulas:

Rather than having variables range over tuples, the variables range over single values from domains of attributes. To form a relation of degree n for a query result, we must have n of these domain variables— one for each attribute.