A planning concept in which planning data is handled in the form of orders. In order planning, supply is planned in the form of planned orders. LN takes into account the start and finish dates of individual planned orders. For production planning, this method considers all material and capacity requirements, as recorded in an item's BOM and routing. These planned orders can be firmed, confirmed and transferred into execution level orders (purchase, production and warehouse transfers). Transferring the planned order means: execution order gets created and planned order gets deleted. Identifier of planned order and execution order do not match, they are separate entities. The Purchase Order Header contains information that applies to the entire purchase order. This Component is required. The Purchase Order Line indicates the ordered item or product ordered along with the quantity, price and other descriptive information. It is also possible to provide additional Parties, PaymentTerms, Charge, and Attachment information as needed at the line level. At least one occurrence of this Component is required for each occurrence of the Purchase Order. The Component Subline represents any additional information concerning the product on the Line. The Subline can be used to describe a specific configuration of the ordered item. The Component Schedule represents the requested ship or delivery dates for goods ordered. The Schedule is an optional Component. The Schedule can not be associated with a Subline. It is only associated with a Line. The schema type for PurchaseOrder. MAKE ALL CHANGES TO ORDER, NOT PO! PurchaseOrder's base abstract type, Order, is shared between PurchaseOrder and SalesOrder. SalesOrder is essentially an extension of PurchaseOrder, but in order to use the local-global design pattern, each of PO and SO needs to instantiate its own Header and Line elements.To do this, we factored out the PO content models, instantiated both PO and SO from Order. This amount is used to override the amount on the line. When omitted the unit price is the same as the unit price for the line.