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Example of association decomposition (SysML)
When designing a system, Systems Engineers will often start with a high level design showing interconnections (associations) between Blocks.
It is only later that the Systems Engineer would start decomposing these associations to further document and detail the connection. The method of implementing this is through the use of Association Blocks. An Association Block is an extension of Association Class in UML. An Association Block Classifier inherits from Blocks and Associations. This means that the internal structure of the Association Block can be represented through an Internal Block Diagram as would be done for a normal Block. In this example we show the Cable connections between the three Blocks in our system including the Pins that they own to enable the connections.
The following Internal Block Diagram shows the connections between the Fuel Pump and the Engine Controller in a very basic form.
SysML introduces a new type of property here called Participant Property. This is a property of the Association that represents the instances that are being connected together. The end attribute of the Participant Property contains the reference to that instance.
Of course the connection between the Engine Controller and Fuel Pump is likely to be much more complex. The following Block Definition Diagram shows the structure of a 2 pin J Connector. The Connector has male and female parts that join together. These contain male and female pins that connect together inside the connectors. MalePin and FemalePin are specializations of a Pin Block. Pins may be connected together using CopperWire.
The initial Block Definition Diagram can now be enhanced to give a more accurate representation of the connections.
The Internal Block Diagram for the J5 Cable can now be updated to show the more complex relationships.
The Internal Block Diagram for the J6 Cable can be updated in the same way (notice the different internal connections).