In Relational Model, which type of constraint does not allow composite and…

In the relational model, every attribute is defined over a domain: the set of atomic (indivisible) and single-valued permissible values for that attribute. A domain constraint requires every attribute's value to be drawn from such an atomic domain, which is exactly what excludes composite attributes (attributes built from sub-parts) and multivalued attributes (attributes holding more than one value at once).

Applying this here: among the given constraint types, only a domain constraint restricts what an attribute's domain may look like at the value level. Because a relational attribute's domain must contain atomic values only, any composite or multivalued attribute coming from an ER design must be decomposed into atomic attributes, or moved into a separate relation, before it can satisfy this constraint. So domain constraints are the rule that disallows them.

The other constraint types govern different things entirely:

• Entity integrity constraint: requires a relation's primary key to be unique and not NULL. It says nothing about whether an attribute's domain is atomic.

• Referential integrity constraint: requires a foreign key value to match an existing primary key value in the referenced relation, or be NULL. It governs cross-relation consistency, not attribute structure.

• Uniqueness (key) constraint: requires values of a candidate-key attribute to be distinct across tuples. It says nothing about atomicity either.

So the constraint that disallows composite and multivalued attributes is the domain constraint.