For example, XML schema includes an annotation element.
Within an annotation you can specify documentation and appinfo (conceptually like a processing instruction but specific to a node or type).
This makes writing custom applications that process XML documents straightforward, and means that a standards-compliant XML Schema processor is part of the XDK on every operating system where Oracle is ported.
The XML Schema processor enables validation of XML and retrieval of metadata.
The course also covers XML serialization according to XML Schema and the tight coupling between XML and ADO. It includes a practical discussion of performance tradeoffs for various XML technology alternatives.