A project contract installment is the amount invoiced to the customer when the related project completes its corresponding element/activity or reaches a milestone or progress of elements/activities. Each BOD message contains the set of installments for a certain project contract line. The customer party of a set of installments is the same as defined for the project contract line. A project contract deliverable header represents the actual delivery, and groups a set of contract deliverable schedule lines that represent partial deliveries. The project contract deliverable line represents a partial delivery, as part of a deliverable schedule.