The "Unique" tag defines a uniqueness constraint on an element. The uniqueness constraint generally applies to the value of an attribute or to the text contained in a tag.

Unique: modeled by a constraint of the "XSD Uniqueness" stereotype, and by a constraint type that is set to "unique". This constraint is connected to the class role (element) to be constrained.

The "Selector" tag defines the path for accessing the constrained fields.

"Field" defines the constrained attributes or elements. These attributes or elements are accessed by following the path defined by "Selector".

These tags are modeled by the XSD Constraint text field for the constraint.

Refer to "XSD reverse generation: Annotation (Documentation - AppInfo)".

The "Key" tag defines a uniqueness constraint on an element. It has the same role as "Unique", but in addition, you can reference it as a foreign key. The uniqueness constraint generally applies to the value of an attribute or to the text contained in a tag.

"Key" is modeled by a constraint of the "XSD Key" stereotype. The constraint has no associated type. This constraint is connected to the class role (element) to be constrained.

These tags are modeled by the "XSD Constraint" text field of the constraint.

The "KeyRef" tag defines a constraint on an element that takes its values from elements subject to another "Key" constraint.

"KeyRef" is modeled by a constraint of the "XSD KeyReference" stereotype. The constraint has no associated type. This constraint is connected to the class role (element) to be constrained.

These tags are modeled by the "XSD Constraint" text field of the constraint.