represents any constraint on the number of members in each value of an EXPRESS aggregation type that appears in the syntactic designation for the type. A SizeConstraint represents either an upper-bound or a lower-bound; in the case of an ARRAY type, the value (hi-index - lo-index + 1) is both the lower-bound value and the upper-bound value. A SizeConstraint is a DomainConstraint, considered to have an equivalent Boolean expression using the built-in SizeOf() function.

represents a constant value specifying the (upper or lower) bound on the number of members in a valid instance of the aggregation type. This attribute is present when the bound expression is a "constant".