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' 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' 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.