In our OES 10g environment there is an application policy xml which is around 2 MB size containing around 35k lines. So it is a nightmare to edit the xml for any attributes or policies for syntax issues. However there are editors such as Eclipse to validate the xml document which may not produce expected results.
So here is an easy way:
Download the OES XSD from this link. The OES 10g documentation has link ( http://www.oracle.com/technology/products/ id_mgmt/oes/ales_policy_propagation_schema.zip) but does not provide the zip file.
There are many online xml validators against a XSD file, one of them is here. You would need to input xml content and xsd content and it will return if there are any errors. One such example of syntax error is shown in below screenshot.
Kudos to my colleague (Aravind Suresh) for exploring this option instead of manually looking for error in xml file, so writing this on his behalf :).