represents an EXPRESS INVERSE attribute = a property of each instance of this entity data type that represents a relationship between them and instances of some other entity data type, where the relationship is modeled as an attribute of the other entity data type.

True if the designated relationship between this instance and any given instance can occur at most once; False if it can occur more than once.

represents the appearance of a lower-bound constraint in syntactic designation for the aggregation type. For this purpose the appearance of an explicit zero ('0') value may be considered to represent no lower-bound constraint; and the lower-bound relationship need not appear. (The appearance of a lower-bound expression that may evaluate to zero shall always be represented by a lower-bound relationship.)

represents the appearance of an upper-bound constraint in syntactic designation for the aggregation type. For this purpose the appearance of an explicit indeterminate value ('?') is considered to represent no upper-bound constraint, and shall not be represented by an upper-bound relationship. (The appearance of an upper-bound expression that may evaluate to '?' shall be represented by an upper-bound relationship.)