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Re: issue 85 - range unit extensions

From: Julian Reschke <julian.reschke@gmx.de>
Date: Tue, 05 Aug 2008 18:21:36 +0200
Message-ID: <48987E10.2040907@gmx.de>
To: Mark Nottingham <mnot@mnot.net>
CC: HTTP Working Group <ietf-http-wg@w3.org>

Mark Nottingham wrote:
> ...
> Straw-man proposal (not exact text):
> 
> Range-unit extensions SHOULD NOT be specific to any format. This is 
> because caches are allowed to combine ranges from multiple responses, 
> and to serve range requests out of cache; format-specific range units 
> make it less likely that implementations will be able to do this 
> (although there may be exceptions, hence the SHOULD NOT). An 
> informational reference to p6 to highlight this to potential extenders 
> would be a good idea.
> ...

Playing the devil's advocate: is there *any* range unit other than 
"bytes" we can think of that is indeed independent of formats? Right 
now, I can't think of any.

So if we strongly believe in this requirement we should probably 
consider to close this extension point. That being said, maybe that 
requirement is too strong.

 > ...
> We'll also need to determine what the requirements for registration are 
> (standards-track?), and set up the registry.
> ...

That's quite some effort for something where we're not sure whether it's 
going to be used. Should we consider delaying the registry until later?

> Furthermore, Section 6.2 - the BNF says:
> 
>> Content-Range = "Content-Range" ":" content-range-spec
>>
>> content-range-spec      = byte-content-range-spec
>> byte-content-range-spec = bytes-unit SP
>>                           byte-range-resp-spec "/"
>>                           ( instance-length | "*" )
>>
>> byte-range-resp-spec = (first-byte-pos "-" last-byte-pos)
>>                                | "*"
>> instance-length           = 1*DIGIT
> 
> This does not allow other range units to be used. If we keep them, this 
> BNF needs to be changed to something like:
> 
> Content-Range = "Content-Range" ":" content-range-spec
> 
> content-range-spec      = byte-content-range-spec / ext-content-range-spec
> byte-content-range-spec = bytes-unit SP
>                           byte-range-resp-spec "/"
>                           ( instance-length | "*" )
> 
> byte-range-resp-spec = (first-byte-pos "-" last-byte-pos)
>                                | "*"
> instance-length           = 1*DIGIT
> ext-content-range-spec = other-range-unit SP CHAR*

+1

I'm not totally sure we need to fix this for Microsoft's use case (which 
uses "=" instead of SP). It seems to use SEARCH (can somebody contact 
the author of that spec ... ;-), while "Content-Range" seems to apply 
only to GET. Or doesn't it?


> Note that section 6.2 places several requirements on the use of the 
> Content-Range header which assume that byte-ranges are in use; we'd need 
> to adjust the language appropriately.
> 
> Beyond that, I can't see what else we'd need to specify; everything else 
> is unit-specific.
> 
> 
> Thoughts?

My proposal would be to just fix the grammar in 6.2, and restructure 6.2 
so that the "bytes" specific stuff ends up in a subsection 6.2.1, and we 
add a 6.2.2 talking about extensions.

BR, Julian
Received on Tuesday, 5 August 2008 16:22:20 GMT

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