The composite structure diagram allows the modeller to describe the relationships
between elements that work together within a classifier. It is similar to the class
diagram, but shows parts and connectors. The parts are not necessarily classes in
the model and they do not represent particular instances, but they may be roles that
classifiers may play.
The parts are shown in a similar manner to objects. The composite structure diagram
is used to show the runtime architectures of any kind of classifier.
Example:
In the following example, under UML1.x the modeller may have shown in a class diagram a typical
invoice with a header and detail as follows:
Although it is useful to be able to depict it as shown above, the significance of the invoice header
and detail may not have warranted separate class descriptions (Disclaimer. Only for example
purposes). The composite structure diagram lends itself to describing, in this instance, the invoice
as follows:
From this we see the invoice modelled as a class and the header and detail modelled as parts. The
connector and its multiplicity indicate that a header will be a structural part of the invoice and that
one ore more detail parts will be present in an invoice.
The Composite Structure Diagram is also useful in displaying collaborations of classes as they, for
example will realize a use case. The notations used can be as follows:
Example: Collaboration with classes inside
Example: Collaboration connected to classes
An example of how the collaboration may be used:
For the use case:Capture customer, the Clerk will capture the customer, the customer address and
the related customer account. The composite structure diagram for this collaboration may look like
this:
To explicitly show the realization, the following diagram may be used:
