Re: please reivew mobileOK Basic Tests 1.0

Accept headers can be used to specify certain media

 

Hi,

Below are my comments to the resolution:

mikew3.org">mikew3.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. students.cs.uu.nl">http://www.w3.org/mid/4668801F.2090006students.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&quot;>, <?xml-stylesheet?&gt; 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. Backbase employee; www.backbase.com.