Purchase order schema for Example.com. Copyright 2000 Example.com. All rights reserved. This example is "reinforced" with additional W3C schema rules and the addition of embedded Schematron elements (see http://www.ascc.net/xml/resource/schematron/schematron.html). Schematron Validation for an Interface XML Document Root element should be a purchaseOrder shipTo name cannot be blank shipTo street cannot be blank shipTo city cannot be blank orderDate is after a shipDate