The only obvious thing I can mention is that an XML Schema can be used in a LiveCycle application. You can create an xml variable and associate it with an XSD. That's useful of course when processing form data that has been submitted from a PDF Form. But there are many other reasons you might need to pass XML data around within an LC application and such data can be bound to a schema (see the properties of an XML variable). Sorry if that might be too obvious though The point about not being able to use an XSD as the model for a Guide is true. The model needs to be an FML for Guides and FML is not auto generated from XSD.