[occi-wg] HTTP Header Serialization Format, use of Attribute header

[Ralf Nyren]

Yes, I am aware of the problems and thus currently only use the  
comma-separated list format for outgoing data.

But as you said we still have this problem for Category and Link headers  
in any case so I do not see why the specification would try to accommodate  
the web framework, etc problems for just attributes. I mean, the whole  
bootstrap/discovery process depends on the ability to send multiple  
Category headers.

A more solid argument as I see it is one of robustness. With the Attribute  
header we tag all the supplied values as being attributes and nothing  
else. For a client this means it can display unrecognized (vendor)  
attributes to the user and a server can respond with an appropriate error  
message for any attributes it does not support. Without the Attribute  
header unrecognized attributes would just be silently discarded.

regards, Ralf

On Wed, 11 Aug 2010 12:52:51 +0200, Edmonds, AndrewX  
<andrewx.edmonds at intel.com> wrote:

> :-)
>
> Be aware of the multiple header keys aspect e.g.
>
> ...
> Attribute: occi.compute.cores=2
> Attribute: occi.compute.speed=2.4
> ...
>
> My experience is that many web frameworks do not observe 2616 correctly.  
> Taking tomcat and associated frameworks; if I send such a request as  
> above the only header that I will receive is the last one, not all.  
> Web.py also exhibits this same behavior. As a result you will always  
> have to formulate your request as such:
>
> Attribute: occi.compute.cores=2, occi.compute.speed=2.4
>
> This particular issue is not a problem using a request like:
>
> ...
> occi.compute.cores=2
> occi.compute.speed=2.4
> ...
>
> However the issue remains for Link and Category headers.
>
> Andy
>
> -----Original Message-----
> From: Ralf Nyren [mailto:ralf at nyren.net]
> Sent: Wednesday, August 11, 2010 11:43 AM
> To: Edmonds, AndrewX; occi-wg at ogf.org
> Subject: Re: [occi-wg] HTTP Header Serialization Format, use of  
> Attribute header
>
> On Wed, 11 Aug 2010 12:30:41 +0200, Edmonds, AndrewX
> <andrewx.edmonds at intel.com> wrote:
>
>> Speaking from an implementer's point of view (mine) removal of
>> "Attribute:" has made parsing of header key/values easier. Personally, I
>> have no strong tie to either approach.
>
> I would beg to differ on that point :)
> I am also an implementor and using the Attribute header I can just reuse
> the same base functionality as for parsing Category and Link headers.
> Since RFC2616 says multiple header values can be represented both as
> comma-separated lists and multiple header lines the code for parsing this
> with proper escaping of quotes etc will have to be present anyway.
>
> regards, Ralf
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