Re: xmlconcat (was 9.0 release notes done)

Peter Eisentraut wrote:
> On mån, 2010-03-22 at 19:38 -0400, Andrew Dunstan wrote:
>   
>>> 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.
>>     
>>>   
>>>       
>> Right. Can you find a way to do that using the libxml API? I haven't 
>> managed to, and I'm pretty sure I can construct XML that fails every 
>> simple string search test I can think of, either with a false negative
>> or a false positive.
>>     
>
> The documentation on that is terse as usual.  In any case, you will need
> to XML parse the input values, and so you might as well resort to
> parsing the output value to see if it is well-formed, which should catch
> this mistake and possibly others.
>
>   

Actually, I have come to the conclusion that the biggest problem in this 
area is that we accept XML documents with a leading DOCTYPE node at all. 
Our docs state:
   The xml type can store well-formed "documents", as defined by the   XML standard, as well as "content" fragments,
whichare defined by   the production XMLDecl? content in the XML standard.
 

A document with a leading DOCTYPE node matches neither of these rules, 
and when we strip the XMLDecl from a piece of XML where it's followed by 
a DOCTYPE node we turn something that is legal XML into something that 
isn't, even by our own (or possibly the standard's) relaxed definition. 
A doctypedecl can only follow an  XMLDecl, see 
<http://www.w3.org/TR/2006/REC-xml11-20060816/#sec-prolog-dtd>.

So I think we need to go back to the drawing board a bit, rather than 
patch a particular reported error case. But these problems are not at 
all new to 9.0, and coming up to beta as I hope we are is not the time 
for it. I think it will have to wait to 9.1.

cheers

andrew