This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
To have a broader picture of what are the validation errors you may expect to receive, you can use an Eclipse IDE or any other tool which has a capability of handling XML files ( Rational Application Developer or MyEclipse or XMLSpy etc.) and place respective DTD or Schema or even simply the XML. And you can validate the XML by right clicking on the xml file. The IDE will validate the XML and provide you the success / warning or Error messages upon validating the XML.