Context : correction of XML file (not creation).
Multiple external commands coud give important reports, for example
* Relax-NG validation with jing
* Xmllint correctness
* Schematron XSLT rules
* SAX extraction of indexed values in a specific tag
It could be very useful to fastly go to the right line (and char ?) of the edited XML file where a script discover an error.
The Scite text editor implements this kind of feature, very useful, except that it is not an XML editor.