Re: [xml-dev] DOCTYPE declaration in the document prolog

>Is following XML sample valid?

No.

>My understanding was that the root element should
>also be declared in the internal declaration subset
>if there is no external declaration subset.

Yes.

>Where can I find clear information about this?

The XML spec.  In particular, the validity constraint "Element Valid"
in section 3.  The root element is no different from any other in this
respect.

-- Richard