Beware that the DITA Open Toolkit, at least the ones included with XMetaL, choke on ditaval files that have a doctype declaration. This limitation is why we decided to not include an authoring customization for them at this time.
Okay, that is interesting to know. However, most of our customers does not use DITA OT at all, but in future this is good thing to know. I assume, that you mean DITA OT 2.2.x? And I have to add, that I already tested ditaval topic making with XMetal and it worked great (topic is created in Content Management System and schema and file are sent to the XMetal editing).