The definition of "Act of Employment" is "An Act of Association wherein an Organization assigns a set of activities to some Person to be performed in exchange for financial compensation." However, this is too narrow. Individuals can also employ individuals.
I suggest changing the label of this class to "Act of Employment by an Organization" and creating a superclass Act of Employment with the following definition.
"An Act of Association wherein an Agent assigns a set of activities to some Person to be performed in exchange for financial compensation."