A property is a nested structure within a classifier, which is 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.
To demonstrate properties, consider the following diagram, which demonstrates some properties of the Library Class.
There are two Parts, libBooks and records, which are instances corresponding to the Classes Books and Computer respectively. After dragging Parts from the Toolbox out to the workspace, right-click on a Part and select the Advanced | Set Property Type context menu option to connect to a classifier.
If Parts disappear when dragged onto the Class, adjust the Z-order of the Class (right-click on it and select the Z-Order context menu option).
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. 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, right-click on the Part and select the Advanced | Custom Properties context menu option. Set the IsReference option to true.
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. This alternative representation is shown in the following diagram. However, this depiction fails to express the ownership immediately reflected by containing properties within a classifier.