The actual cost of labor entails evaluating the number of hours spent by real people on real tasks. In this model, the Persons involved are presumed to be holders of Employment (that is, employees). Specifically, the model in Figure 16-10 asserts that each Labor Usage (that is something like a time-sheet entry) must be of one and only Employment (that is, a Person that is a holder of Employment with an Organization. If this is not the case, then the relationship could be generalized to say that each Labor Usage must be of one and only one Person.

Just as material costs were calculated based on the quantity of material used, the cost of labor is based on the Hours Worked of an Employment (that is, by an employee), charged to ...

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