Class UML 2.4.1::Extension

Description:

An extension is used to indicate that the properties of a metaclass are extended through a stereotype, and gives the ability to flexibly add (and later remove) stereotypes to classes.

Direct Superclasses: Association

Direct Subclasses:

Class Precedence List: Extension, Association, Classifier, Namespace, Type, PackageableElement, ParameterableElement, RedefinableElement, NamedElement, TemplateableElement, Relationship, Element

Properties:

isRequired : Boolean (1 1); -- source Extension

Indicates whether an instance of the extending stereotype must be created when an instance of the extended class is created. The attribute value is derived from the value of the lower property of the ExtensionEnd referenced by Extension::ownedEnd; a lower value of 1 means that isRequired is true, but otherwise it is false. Since the default value of ExtensionEnd::lower is 0, the default value of isRequired is false.
{readonly, derived}
Default value: FALSE

metaclass : Class (1 1); -- source Extension
ownedEnd : ExtensionEnd (1 1); -- source Extension
endType : Type (1 *); -- source Association
isDerived : Boolean (1 1); -- source Association
memberEnd : Property (2 *); -- source Association
navigableOwnedEnd : Property (0 *); -- source Association
attribute : Property (0 *); -- source Classifier
collaborationUse : CollaborationUse (0 *); -- source Classifier
feature : Feature (0 *); -- source Classifier
general : Classifier (0 *); -- source Classifier
generalization : Generalization (0 *); -- source Classifier
inheritedMember : NamedElement (0 *); -- source Classifier
isAbstract : Boolean (1 1); -- source Classifier
isFinalSpecialization : Boolean (1 1); -- source Classifier

If true, the Classifier cannot be specialized by generalization. Note that this property is preserved through package merge operations; that is, the capability to specialize a Classifier (i.e., isFinalSpecialization =false) must be preserved in the resulting Classifier of a package merge operation where a Classifier with isFinalSpecialization =false is merged with a matching Classifier with isFinalSpecialization =true: the resulting Classifier will have isFinalSpecialization =false.
Default value: FALSE

ownedTemplateSignature : RedefinableTemplateSignature (0 1); -- source Classifier
ownedUseCase : UseCase (0 *); -- source Classifier
powertypeExtent : GeneralizationSet (0 *); -- source Classifier
redefinedClassifier : Classifier (0 *); -- source Classifier
representation : CollaborationUse (0 1); -- source Classifier
substitution : Substitution (0 *); -- source Classifier
templateParameter : ClassifierTemplateParameter (0 1); -- source Classifier
useCase : UseCase (0 *); -- source Classifier
elementImport : ElementImport (0 *); -- source Namespace
importedMember : PackageableElement (0 *); -- source Namespace
member : NamedElement (0 *); -- source Namespace
ownedMember : NamedElement (0 *); -- source Namespace
ownedRule : Constraint (0 *); -- source Namespace
packageImport : PackageImport (0 *); -- source Namespace
package : Package (0 1); -- source Type
visibility : VisibilityKind (1 1); -- source PackageableElement
owningTemplateParameter : TemplateParameter (0 1); -- source ParameterableElement
isLeaf : Boolean (1 1); -- source RedefinableElement
redefinedElement : RedefinableElement (0 *); -- source RedefinableElement
redefinitionContext : Classifier (0 *); -- source RedefinableElement
clientDependency : Dependency (0 *); -- source NamedElement
name : String (0 1); -- source NamedElement
nameExpression : StringExpression (0 1); -- source NamedElement
namespace : Namespace (0 1); -- source NamedElement
qualifiedName : String (0 1); -- source NamedElement
templateBinding : TemplateBinding (0 *); -- source TemplateableElement
relatedElement : Element (1 *); -- source Relationship
ownedComment : Comment (0 *); -- source Element
ownedElement : Element (0 *); -- source Element
owner : Element (0 1); -- source Element

Constraints:

Signature: non_owned_end() : Boolean;
Description: The non-owned end of an Extension is typed by a Class.
The OCL used here is not normative.
Editor's notes: metaclass, not metaclass(). Classifier, not class
Expression: metaclass->notEmpty() and metaclass.oclIsKindOf(Classifier)
Original: metaclassEnd()->notEmpty() and metaclass()->oclIsKindOf(Class)

Signature: is_binary() : Boolean;
Description: An Extension is binary, i.e., it has only two memberEnds.
Expression: memberEnd->size() = 2

Operations:

Signature: metaclassEnd() : Property;
Description: The query metaclassEnd() returns the Property that is typed by a metaclass (as opposed to a stereotype).
The OCL used here is not normative.
Editor's notes:
Expression: result = (memberEnd - OrderedSet{ownedEnd}).asOrderedSet()->first()
Original: result = memberEnd->reject(ownedEnd)

Signature: metaclass.1() : Class;
Description: The query metaclass() returns the metaclass that is being extended (as opposed to the extending stereotype).
Expression: result = metaclassEnd().type

Signature: isRequired.1() : Boolean;
Description: The query isRequired() is true if the owned end has a multiplicity with the lower bound of 1.
Expression: result = (ownedEnd->lowerBound() = 1)

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