A tagged value is consists of a tag-value pair and is attached to an element to hold some piece of information.

a combination of a tag and a value that gives supplementary information that is attached to a model element

a keyword-value pair that may be attached to any kind of model element (including diagram elements as well as semantic model elements)

an extensibility mechanism that allows you to create new information about model element s and presentation element s

an extension of the properties of a UML element

a property-value pair that may be defined by the user

a (Tag, Value) pair that permits arbitrary information to be attached to any model element

The explicit definition of a property as a name-value pair. In a tagged value, the name is referred as the tag. Certain tags are predefined in the UML; others may be user defined. Tagged values are one of three extendibility mechanisms in UML. See: constraint, stereotype.