[DAS] Re: RFC DAS-Headers

[Thomas Down]

On Mon, Nov 26, 2001 at 05:46:15PM -0500, Brian Gilman wrote:
> Hello,
> 
> 	I agree with this. I'm just worried about the poor DAS 1.0
> implementors who need to understand what kind of XML document they are
> getting and what doc handler to instantiate. That's all implemtation
> detail though. 
> 
> 	If we are dicussing DAS 2.0 we can add the XML schema type,
> version and name to the SOAP headers. I have to problem with that at all. 

I guess that's possible (although not quite the `normal'
interpretation of SOAP Headers -- they're usually used to
provide a context for the core message, things like transaction
IDs).  But I still don't really see why it's needed.  The schema
in force (and therefore the appropriate parser to use) should
be clear from the (qualified) names of the elements you
recieve.

I can see that, if you're parsing a whole XML document using
something like SAX, it can be useful to know what's happening
in advance.  But I can't see anyone handling SOAP messages this
way.  The first-generation SOAP toolkits all used DOM to hold
the complete message before decoding, so it's easy to pass
sub-trees of the document off to separate parsing code.
Axis /does/ do event-based parsing of SOAP messages, but it has
a dedicated framework for delegating the handling of subtrees.
So again, I don't see any problem with switching parsers based
on QNames of elements.  [Aside: I've been using Axis quite heavily
for the last few days, and it's pretty nice.  The Deserializer
system is similar to StAX in principle, if not in detail].

I'd strongly suspect that anyone else who does an event-driven
SOAP toolkit would follow similar patterns.


Or am I missing something here?

    Thomas.