The document provides a step-by-step guide for modeling a business process diagram (BPD) for a distilled water delivery service, beginning with customer order placement and involving customer identity verification. It outlines the creation of tasks, gateways, intermediate events, and sub-processes necessary for accurately representing the flow of the delivery process, including actions taken based on whether the customer is new or returning. The final steps include creating tasks for logistics and delivery, culminating in an end event to signify the completion of the process.