W3C home > Mailing lists > Public > uri@w3.org > November 2009

Re: URI Template: expanding lists

From: Roy T. Fielding <fielding@gbiv.com>
Date: Fri, 6 Nov 2009 11:29:30 -0800
Cc: Christophe Lauret <clauret@weborganic.com>, uri@w3.org, Mark Nottingham <mnot@mnot.net>, Joe Gregorio <joe@bitworking.org>
Message-Id: <27222E21-121B-45A6-B546-5C9D02AAF294@gbiv.com>
To: Bob Aman <sporkmonger@gmail.com>
On Nov 5, 2009, at 10:52 PM, Bob Aman wrote:

>> [Comment on the URI Template working draft]
>>
>> Is there any particular reason why the current draft suggests that
>> variables typed as lists (marked with @) be expanded so that the
>> variable name is followed by a generated numbering?
>>
>> The numbering scheme seems quite odd and specific (1-based with first
>> item unnumbered).
>>
>> For example, in the case of the ? operator:
>>
>>  {?@list}  ?list=val1&list2=val2&list3=val3
>>
>> Why not simply expand it as:
>>
>>   ?list=val1&list=val2&list=val3
>>
>> This would still be a perfectly valid sequence of query parameters.
>> Or am I missing something obvious?
>
> I think the obvious objection is that many web frameworks (php, rails,
> app engine, etc) make the assumption that query parameter keys are
> unique, so method calls like `request.params["list"]` would probably
> return `val3` with no means of obtaining the array order or other
> values in the array without parsing the request URI manually.  That
> said, I don't think the obvious objection is a good reason to choose
> what strikes me as the slightly less elegant option, and I would much
> prefer your expansion to the current one.  URI templates aren't
> necessary to the function of every web application, frameworks can
> slowly adapt, and in the meantime, manually parsing the URI when
> necessary is fine with me.

Yes, it matches the obvious limitation in HTML and all of the
libraries that pre-parse query parameters into hash tables.
The names must be unique.  More importantly, something like

    form.cgi{?name,@address}

is such a common idiom that I figured it was worth capturing
in a short form.  Almost all examples I've seen using that
kind of form use address, address2, address3 as the names.

However, I don't think this is a necessary feature for
uri-templates, so we could just remove it if folks disagree.

....Roy
Received on Friday, 6 November 2009 19:29:58 UTC

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