Entity-Relationship Diagram (ERD)

"In business or commerce, an order is a stated intention, either spoken or written, to engage in a commercial transaction for specific products or services. From a buyer's point of view it expresses the intention to buy and is called a purchase order. From a seller's point of view it expresses the intention to sell and is referred to as a sales order. When the purchase order of the buyer and the sales order of the seller agree, the orders become a contract between the buyer and seller.
Within an organization, the term order may be used to refer to a work order for manufacturing, a preventive maintenance order, or an order to make repairs to a facility.
In many businesses, orders are used to collect and report costs and revenues according to well-defined purposes. Then it is possible to show for what purposes costs have been incurred." [Order (business). Wikipedia]
The BPMN 2.0 (Business Process Model and Notation) diagram example "Order process" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Business Process Diagram solution from the Business Processes area of ConceptDraw Solution Park.

This purchase order processing UML activity diagram was created on the base of activity diagram from the software architecture documentation wiki of the Software Engineering Institute (SEI) of Carnegie Mellon University (CMU).
[wiki.sei.cmu.edu/ sad/ index.php/ Image:PurchaseOrderActivityDiagram.png]
"A purchase order (PO) is a commercial document and first official offer issued by a buyer to a seller, indicating types, quantities, and agreed prices for products or services. Acceptance of a purchase order by a seller forms a contract between the buyer and seller, so no contract exists until the purchase order is accepted. It is used to control the purchasing of products and services from external suppliers.
Creating a purchase order is typically the first step of the purchase to pay process in an ERP system." [Purchase order. Wikipedia]
This purchase order processing UML activity diagram example was created using the ConceptDraw PRO diagramming and vector drawing software extended with the ATM UML Diagrams solution from the Software Development area of ConceptDraw Solution Park.