1. The tuple relational calculus is a nonprocedural language. (The relational algebra was procedural.) We must provide a formal description of the information desired.

2. A query in the tuple relational calculus is expressed as

{t︱P(t)}

i.e. the set of tuples t for which predicate P is true.

3. We also use the notation

• t[a] to indicate the value of tuple t on attribute a.
• t ∈ r to show that tuple t is in relation r.