XML Schema validation in Python

[Medhat.Gayed at gmail.com]

I tested and tried a few XML validators but none of them is able to
successfully validate a string of xml (not a file just a string) to
programatically be able to validate messages of xml that flow in and
out of the different systems.  The validators I used were XSV, oNVDL
and lxml, can we implement a pure python module for validating strings
of xml using XML Schema (not DTD) ?