On sön, 2010-03-21 at 13:07 -0400, Andrew Dunstan wrote:
> Yeah, maybe. According to
> <http://www.w3.org/TR/REC-DOM-Level-1/level-one-core.html> the only
> legal child of an XML Document node that is not also a legal child of a
> DocumentFragment node is a DocumentType node. So we could probably just
> look for one of those in each argument node and strip it out. That
> should be fairly lightweight in the common case where it's not present -
> we'd just be searching for a fixed string. Removing it if found would be
> more complex. We'd have to parse the node to remove it, since a legal
> DocumentType node string could appear legally inside a CDATA node.
According to the SQL/XML standard, the document type declaration should
apparently be stripped when doing a concatenation. (This makes sense
because the result of a concatenation can never be valid according to a
DTD.)
But if we are not comfortable about being able to do that safely, I
would be OK with just raising an error if a concatenation is attempted
where one value contains a DTD. The impact in practice should be low.