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RE: XForms, the xf:header and the HTTP Accept header.

From: Philip Fennell <Philip.Fennell@bbc.co.uk>
Date: Wed, 30 Jul 2008 15:26:17 +0100
Message-ID: <FBFAE0E0B37B4148AF77509764D4BC2007B1E657@bbcxues11.national.core.bbc.co.uk>
To: <www-forms@w3.org>

Aaron,

> we must keep in mind that the accept header by default is what
> the browser will accept back which is certainly a far greater 
> variety than the xforms plugin can accept.  And in most case, 
> I'd argue, the xforms processor has no idea what the user is 
> trying to do so to automatically limit the user seems the wrong way to
go.

Where a submission uses replace="instance", then the developer's intent
is that the response is for the XForms processor. Where replace="all" is
used, the intent is that the response is being handed back to the parent
browser and therefore it should be the developer's responsibility to set
the Accept header accordingly in these contexts. With that in mind, I'd
argue that overwriting the accept header should be the preferred
behaviour as it is possible for the developer to express their intent
through the setting of the submission element's replace attribute.


Regards

Philip Fennell
>XSLT Developer (Content Management Culture)
>
>BBC Future Media & Technology
>Media Village, 201 Wood Lane London W12 7TP 
>BC4 C4, Broadcast Centre
>
>T:	0208 0085318
>

-----Original Message-----
From: www-forms-request@w3.org [mailto:www-forms-request@w3.org] On
Behalf Of Aaron Reed
Sent: 29 July 2008 19:13
To: www-forms@w3.org
Subject: Re: XForms, the xf:header and the HTTP Accept header.


Hi,

Just a FYI to the WG, Mozilla will 'replace' the value of a request
header with the value specified in the xf:header if that particular
header is only capable of containing one value (for example, the content
type header) but will 'append' the value if the header is capable of
containing more than one value.

With regards to Philip's argument that the Accept header should only
contain a single media type and that 'Multiple media types suggest that
the XForm can accept multiple representations', we must keep in mind
that the accept header by default is what the browser will accept back
which is certainly a far greater variety than the xforms plugin can
accept.  And in most case, I'd argue, the xforms processor has no idea
what the user is trying to do so to automatically limit the user seems
the wrong way to go.  Now, in cases where the instance is being replaced
Philip probably has a point.  But in generic post or get submission
scenarios it could be that the user might be trying to get out of xforms
completely if there is a more appropriate type available but is willing
to take xforms in a pinch.

So unless the user has a way to specify his intent (the way he'd do that
would be up to this WG), I'd leave it up to the server to serve down the
appropriate format given the information available to it.

--Aaron

Philip Fennell wrote:
> The Mozilla XForms plug-in now, via nightly builds, has support for 
> the xf:header element and its associated attributes and child 
> elements. With respect to the HTTP Accept header, the Mozilla 
> implementation appends the value in the XForm to the request header 
> whilst, for example, the FormsPlayer implementation overwrites the
existing header.
> 
> After discussion with Aaron Reed on the dev-tech-xforms mailing list 
> he suggests that:
> 
>> Sounds like you have a usecase for the XForms working group to
> consider. 
>> Maybe they could put an attribute on the xf:header that says to
> replace rather than append.
> 
> For my two-penneth worth, after thinking about this for a bit, due to 
> the nature of an XForms request and the fact that any data bindings 
> will only be valid for a single representation of the requested 
> resource, the Accept header should be overridden and therefore only 
> have a single media type. Multiple media types suggest that the XForm 
> can accept multiple representations which is of course highly unlike. 
> How you decide which headers are overridden and which get appended is 
> an interesting question.
> 
> Does anyone on this list have an opinion about this?
> 
> 
> Regards
> 
> Philip Fennell
> 
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Received on Wednesday, 30 July 2008 14:26:55 GMT

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