C validating xml dtd
Its authors might benefit from a remedial course on how to accept run-time parameters from the user.
However, it seems most people on Windows use an XML Editor, such as Notepad (as described in Nate's answer) or XML Notepad 2007 as suggested by Steve C (there are also several commercial editors which I won't mention here).
This is why your system is telling you that your data has a security issue.
To some people, the idea that DTDs are a security risk sounds more like paranoia than good sense, but I don't believe they are correct. The best solution is to complain bitterly to your vendor that they have been suckered by an old wive's tale about XML security, and tell them that if they care about security they should do a rational security analysis instead of prohibiting DTDs.
Remember (a) that a healthy paranoia is what security experts need in life, and (b) that anyone really interested in security would insist on the resource limits in any case -- in the presence of resource limits on the parsing process, DTDs are harmless. Meanwhile, as the message suggests, you can "set the Prohibit Dtd property on Xml Reader Settings to false and pass the settings into Xml Reader.
Create method." If the input is in fact untrusted, you might also look into ways of giving the process appropriate resource limits.
I'm working on some very complicated XML with very complicated rules, and I'm new to this so tracking down which attribute is missing is taking a long time. It can be run from the command line like xmllint and it supports RELAX NG: https://java.net/ I found this online validator from 'corefiling' quite useful - After trying few tools to validate my xsd, this is the one which gave me detailed error info - so I was able to fix the error in schema.