Check it out on OTN.
The System properties (name, value) are defined in the orion-application.xml descriptor provided with the application.
During deployment with ASC, the deployment plan editor can be used to view the set of specified System properties in the application. It can also be used to add, remove, edit the defined properties so they can be tailored to the specific deployment being performed.
<property name="application.tax.rate" value="10" />
<property name="application.tax.code" value="AU" />