An address should have a street. An address should have a city. An address should have a state. An address should have a zip. An address should have a type attribute. The elements is not expected at the top of a document. They form part of an address. A purchase order should have a shipTo element. A purchase order should have a shipDate element. A purchase order should have an Items element. A purchase order should have an orderDate attribute. The element is not expected at the top of a document. It should be in the body of a purchase order. A purchase order element should have a shipping address. There should be a shipTo element contained by the PurchaseOrder element. A shipping address element should have a name element. The Items element can only contain Item elements The Item element should contain a product name. The Item element should contain a quantity element The Item element should contain a price element. A comment should have no subelements A comment can only appear in an Item or a Purchase Order