Binary association dialog box

Binary associations

An association (or aggregation) specifies a stable link between two or more instances or sets of instances, and can be binary or n-ary. Where a binary association is concerned, the association entry dialog box allows the entry of both the association and the association ends.

The "Binary association" dialog box contains four tabs - "Properties", "Notes", "Tagged values" and "Stereotypes". For information on these standard dialog box tabs, please see "Standard dialog box tabs".

The "Properties" tab of the "Binary association" dialog box

The "Properties" tab of the "Binary association" dialog box is used to define values for a binary association.

The "Properties" screen of the "Binary association" dialog box

Key:

· "In the association or the aggregation": This specifies the binary association name.

· "The class": This defines the names of the classes at both ends of the link.

· "Has the role of": This is the role played by the class with regard to the class at the other end of the link.

· "Quantity (min-max)": This is the interval multiplicity written "min*max". "min" gives the minimum number of instances of the class, and "max" indicates the maximum number of instances of the class. The "*" symbol means unlimited.

· "Association kind": This is used to define the kind of association concerned. "Association" is for standard associations, "Aggregation" represents "shared aggregations" (indicated by a white triangle), and "Composition" represents strong composition (graphically shown by a black triangle).

· "Is changeable": When placed on a target end, this specifies whether or not an instance of the association may be modified from the source end.

· "Is navigable": This specifies whether or not the association (which must be binary) can be traversed from the opposite class to the class attached to the association end in question.

· "Accessible the following way": This is the visibility of the member (public, protected or private). Choosing visibility orientates the relation between the current class and the class at the other end (navigability).

· "Access mode": This determines the access mode of the association (read, write, read/write or no access).

· "Abstract": This determines if the role is abstract or not.

· "Class": This determines if the role is class or not.

· "Is ordered": This determines if the role is ordered or not.

· "Is unique": This determines if the role is unique or not.