A property is a nested structure within a classifier, usually a Class or an Interface, on a Composite Structure diagram. The contained structure reflects instances and relationships reflected within the containing classifier. Properties can have multiplicity, and can be displayed as:

·Parts (preferred) or
·Association Roles



In this diagram there are two Parts, libBooks and records, which are instances corresponding to the Classes Books and Computer respectively. The relationship between the two Parts is indicated by the connector, reflecting that communication between the Parts is via the barcode. This contained structure and its Parts are properties owned by the Library Class.

After dragging Parts from the Diagram Toolbox onto the Class, right-click on a Part and select Advanced | Set Property Type to connect to a classifier. If Parts disappear when dragged onto the Class, adjust the Z-order of the Class to move it behind the Parts (right-click on the Class and select the Z-Order context menu option).

To indicate a property that is not owned by composition to the containing classifier, use a box symbol with a dashed outline, indicating association; to do this:

1.Right-click on the Part and select the Properties context menu option.
2.Select the Advanced page of the Properties dialog.
3.Set the IsReference option to true.

Association Roles

Properties can also be reflected using a normal composite structure (without containing it in a Class), with the appropriate connectors, Parts and relationships indicated through connections to the Class.

The alternative representation is shown here; however, this representation fails to express the ownership immediately reflected by containing properties within a classifier.