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Re: please reivew mobileOK Basic Tests 1.0

From: Laurens Holst <lholst@students.cs.uu.nl>
Date: Sun, 30 Sep 2007 12:23:03 +0200
Message-ID: <46FF7907.7030700@students.cs.uu.nl>
To: Jo Rabin <jrabin@mtld.mobi>
CC: mike@w3.org, public-bpwg-comments@w3.org
Jo Rabin schreef:
>
> Laurens
>
>  
>
> Thanks for your further reply on this. Ref RFC2616
>
>  
>
> Accept headers *can* be used to specify certain media
>
> types which are acceptable for the response. …
>
>  
>
> Not “should” or “must”.
>

I think you’re misinterpreting that sentence, it “can” be used because 
the Accept header is optional. It does not imply the Accept header can 
be used differently than described, and that you can just put any kind 
of nonsense in there and still expect it to work.

> And if the server needs to respond with a 3xx, 4xx or 5xx response 
> code, in principle it would not know how to do that if the request did 
> not contain a range of content types.
>

I don’t understand how that would be. Different content types are just 
different representations of data. A single resource can be represented 
by several content types. If you’re going to indicate to the server that 
you accept certain representations, then the server can send any of 
them. However regardless of the content type, the server knows perfectly 
well when a response of 3xx, 4xx or 5xx is needed for that resource 
(e.g. when it has moved or is unavailable). They’re two separate things, 
and unrelated.

I do not understand the resistance against just sending the correct 
Accept headers. That is how the protocol is designed, and it’s also how 
browsers implement it.

Also, you’re completely glossing over my statement that sending 
incorrect Accept headers *breaks* servers which correctly handle content 
negotiation, because the accepted content types are not correctly 
indicated by the test. Thus, with this test the W3C would force web 
sites to not use content negotiation if they want to get your label for 
‘correctness’.


~Grauw

> ------------------------------------------------------------------------
>
> *From:* public-bpwg-comments-request@w3.org 
> [mailto:public-bpwg-comments-request@w3.org] *On Behalf Of *Laurens Holst
> *Sent:* 29 September 2007 19:01
> *To:* mike@w3.org
> *Cc:* public-bpwg-comments@w3.org
> *Subject:* Re: please reivew mobileOK Basic Tests 1.0
>
>  
>
> Hi,
>
> Below are my comments to the resolution:
>
> mike@w3.org <mailto:mike@w3.org> schreef:
>
>  Dear Laurens Holst ,
>  
> The Mobile Web Best Practices Working Group has reviewed the comments you
> sent [1] on the Last Call Working Draft [2] of the W3C mobileOK Basic
> Tests 1.0 (2nd Last Call) published on 25 May 2007. Thank you for having
> taken the time to review the document and to send us comments!
>  
> The Working Group's response to your comment is included below, and has
> been implemented in the new version of the document available at:
> http://www.w3.org/TR/2007/WD-mobileOK-basic10-tests-20070928/.
>  
> Please review it carefully and let us know if you agree with it or not
> before 19 October 2007. In case of disagreement, you are requested to
> provide a specific solution for or a path to a consensus with the Working
> Group. If such a consensus cannot be achieved, you will be given the
> opportunity to raise a formal objection which will then be reviewed by the
> Director during the transition of this document to the next stage in the
> W3C Recommendation Track.
>  
> Thanks,
>  
> For the Mobile Web Best Practices Working Group,
> Michael(tm) Smith
> W3C Staff Contact
>  
>  1. http://www.w3.org/mid/4668801F.2090006@students.cs.uu.nl
>  2. http://www.w3.org/TR/2007/WD-mobileOK-basic10-tests-20070525/
>  
>  
> =====
>  
> Your comment on 2.3.2 HTTP Request:
>   
>> First, section 2.3.2 HTTP Request states:
>>  
>>     
>>>    *
>>>  
>>>       Include an |Accept| header indicating that Internet media
>>>       
>> types
>>     
>>>       understood by the default delivery context are accepted by
>>>       sending exactly this header:
>>>  
>>>       Accept:
>>>       
> application/xhtml+xml,text/html;q=0.1,application/vnd.wap.xhtml+xml;q=0.1,text/css,image/jpeg,image/gif
>   
>>>             
>>>  
>>>       
>> I think this is incorrect, text/css should NOT be included in the
>> Accept 
>> header, and image/jpeg and image/gif ONLY if the UA is expected to 
>> support showing these images independantly of a document (the mobileOK
>>  
>> tests should explicitly check whether this is supported). The client 
>> after all does not know how to handle a text/css file independently of
>>  
>> XML markup.
>>  
>> Instead, it should send an "Accept: text/css" header when the CSS files
>>  
>> that are linked using <link rel="stylesheet">, <?xml-stylesheet?> or 
>> @include. Similarly, images referenced from <img> should send an 
>> "Accept: image/jpeg,image/gif" header. Aside from checking the Accept 
>> header for the main page, the mobileOK tests should also check that 
>> Accept headers send these values for stylesheet and image requests.
>>     
>  
>  
> Working Group Resolution:
> We do not think it is wrong to specify the headers in the way we do,
> however we accept that we do not properly check that the right sort of
> content has come back in response to the request. In other words, if the
> request is made because of an img tag then the response should be an
> image. We did not test for that in the draft you reviewed and we will
> amend accordingly. In particular, in 3.4, <img> tags that retrieve valid
> CSS delivered as text/css should for example FAIL too.
>   
>
>
> I do not think this is the correct resolution (although it is good 
> that the test now also checks the response).
>
> The reason for this is that in your HTTP request you say that a file 
> can be delivered in all the formats specified by the Accept header. 
> Thus, if the server sends you a text/css file, it can not lead to FAIL 
> because you asked for it.
>
> Quote from the HTTP specification RFC 2616 section 14.1:
>
> The Accept request-header field can be used to specify certain media
> types which are acceptable for the response. Accept headers can be
> used to indicate that the request is specifically limited to a small
> set of desired types, as in the case of a request for an in-line
> image.
>   
>
>
> Checking in the UA (in this case, the test) for whether something is 
> an image and throwing an error, but at the same time saying in the 
> HTTP headers that you *do* accept non-images is inconsistent and 
> incorrect. You are sending false information to the server. What’s 
> worse, sites which *correctly* implement content negotiation properly 
> and e.g. send text/css *according to the request*, will get a FAIL on 
> your test.
>
> The solution you propose breaks content negotiation as specified in 
> RFC 2616 and is not acceptable.
> The solution I provide is to send the following HTTP header for 
> requests resulting from <img> tags: Accept: image/jpeg,image/gif
> An alternative solution is to not send an Accept header at all.
>
>
> ----
>  
> Your comment on 2.3.2 HTTP Request:
>   
>> Third, in that same section, there is a requirement that only HTTP GET 
>> methods can only be used. What about form submissions with POST?
>> Forcing 
>> forms to be sent with the GET method seems undesirable and impairs the
>>  
>> HTTP functionality. It seems a silly limitation too, because if a 
>> mobileOK Basic application must support HTTP and HTTPS, and Basic and 
>> Digest HTTP authentication, then surely support for POST would be 
>> trivial. The mobileOK tests should provide tests for checking proper 
>> cache clearing after a POST request has been done on a URL.
>>     
>  
>  
> Working Group Resolution:
> We will insert a reference in 2.3.2 referring to 2.3.8 to make it clearer
> that POST is definitely allowed as a form action in mobileOK content but
> that it is simply not tested, for fear of the tester causing unwanted side
> effects.
>   
>
>
> Great.
>
>
> ----
>  
> Your comment on 3.4 CONTENT_FORMAT_SUPPORT and VALID_MARKUP:
>   
>> Fifth, in 3.4 CONTENT_FORMAT_SUPPORT  and VALID_MARKUP it does not 
>> distinguish included resources by type, that is, if it’s a stylesheet
>>  
>> include, only the text/css media type should be accepted (otherwise 
>> FAIL), and if it’s an image include, only image/gif or image/jpeg is
>>  
>> accepted and not text/css. If it’s an object include, unless the UA
>> is 
>> expected to support CSS there by showing it somehow, text/css should 
>> also not be accepted.
>>     
>  
>  
> Working Group Resolution:
> We will add that if the resource is expected to be a stylesheet, it must
> be text/css (and be valid CSS), and likewise for images and FAIL if it is
> not - also that Objects need to be images in this case.
>   
>
>
> Great.
>
>
> Regards,
>
> ~Grauw
>
> -- 
> Ushiko-san! Kimi wa doushite, Ushiko-san nan da!!
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Laurens Holst, student, university of Utrecht, the Netherlands.
> Website: www.grauw.nl <http://www.grauw.nl>. Backbase employee; www.backbase.com <http://www.backbase.com>.


-- 
Ushiko-san! Kimi wa doushite, Ushiko-san nan da!!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Laurens Holst, student, university of Utrecht, the Netherlands.
Website: www.grauw.nl. Backbase employee; www.backbase.com.


Received on Sunday, 30 September 2007 10:23:24 GMT

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