Type : "string"
omposition of an Expression that states the abstraction relationship between the supplier and the client. In some cases, such as Derivation, it is usually formal and unidirectional;in other cases, such as Trace, it is usually informal and bidirectional. The mapping expression is optional and may be omitted if the precise relationship between the elements is not specified.Semantics Depending on the specific stereotype of Abstraction, the mapping may be formal or informal, and it may be unidirectional or bidirectional. Abstraction has predefined stereotypes (such as «derive», «refine», and «trace») which are defined in the Standard Profiles chapter. If an Abstraction element has more than one client element, the supplier element maps into the set of client elements as a group. For example, an analysis-level class might be split into several design-level classes. The situation is similar if there is more than one supplier element.