W3C home > Mailing lists > Public > public-html@w3.org > June 2007

Re: please reivew mobileOK Basic Tests 1.0

From: Sean Owen <srowen@google.com>
Date: Sun, 10 Jun 2007 19:09:21 -0400
Message-ID: <e920a71c0706101609w1556deb7u4dd160dddcf65791@mail.gmail.com>
To: "Laurens Holst" <lholst@students.cs.uu.nl>
Cc: public-bpwg-comments@w3.org, "public-html@w3.org" <public-html@w3.org>

Thanks Laurens, we appreciate the comments. Here are some comments and
replies that I gathered from group discussion.

On 6/7/07, Laurens Holst <lholst@students.cs.uu.nl> wrote:
>  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.

It's an interesting point. RFC 2616 says in 14.1 that Accept *can*
indicate desired types this way, and 10.4.7 says that servers can even
return a type not listed in the Accept header in some cases. I bring
it up to make the point that Accept seems to be advice, and doesn't
have to exactly enumerate acceptable types.

It seems standard practice that user agents send a fixed string
listing all of what they support each time.

Finally it's conceivable that one might vary a document a little bit
based on other types in the Accept header, like linking to JPEG versus
PNG images in an <img> tag. I don't know that this is at all common
though.

If it's not wrong, and mimics real-world user agents a little more,
we'd very slightly prefer to keep the fixed Accept header as-is.


>  Second, in that same section, I think saying that UAs must send 'exactly'
> this header is not desirable. That would prevent UAs from handling
> additional media types, such as image/png or image/svg, and limit
> innovation. After all, the UA would not be able to claim a mobileOK label
> anymore. The spec should say that UAs must send exactly this or a superset
> of this header.

mobileOK Basic tests whether a resource can be delivered in a way that
is compatible with an abstract baseline device profile, the "Default
Delivery Context". This profile only assumes GIF and JPEG support, so
it would be undesirable for a mobileOK Basic tests implementation to
send a header that says that PNG is supported. The test demands that
you demonstrate support or GIF or JPEG, so it doesn't help to add more
types.

But this is not to say that mobileOK resources can't return PNG or SVG
images to other real devices! mobileOK Basic says nothing about what
you do for more capable devices. It merely wants to see that you can
support a certain basic device that only knows JPEG and GIF.


>  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.

Yes, mobileOK Basic resources are welcome to use POST and HTTPS. The
tests only use GET, and do not test URLs that require the POST method,
but this is not the same as saying this is prohibited.

The reasoning is that POST may have side effects and we don't want the
tester to harm servers. We should spell out this reasoning more
clearly, in section 2.3.2.


>  Fourth, section 2.3.4 Meta http-equiv Elements: why are these supported at
> all, especially Content-Type and Cache-Control? In section 3.3, a <meta>
> element is listed as an option to indicate character encoding, given that
> there is an XML declaration and this <meta> only complicates character set
> detection, I do not see a reason for allowing this.

Good question. This would only apply in the case where there was no
character encoding in the HTTP headers. In this case some user agents
will look for and use values in a <meta> tag, even though this is not
a preferred way to specify character encoding. Getting character
encoding right is essential, so this recommendation is there so that
resources are better "safe than sorry", even though it's possibly
redundant.


>  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.

Yes, this seems like a reasonable tightening of the test. We will add
something along these lines -- if the resource is expected to be a
stylesheet, it must be text/css (and be valid CSS), and likewise for
images.


>  Sixth, in 3.10 LINK_TARGET_FORMAT, it states:
>
>
> If the Content-Type header value of the HTTP response is not consistent
> (determined in the same way as specified in 3.3 CHARACTER_ENCODING_SUPPORT
> and CHARACTER_ENCODING_USE) with the Accept-Charset header in 2.3.2 HTTP
> Request, warn
>  This should be a FAIL condition. Character set mismatches are very
> undesirable (especially from an i18n perspective) and will create
> significant hindrances for most non-English users, whose languages have
> accents or even do not use our alphabet at all.

>From my reading of RFC 2616, 14.2, it's allowed to send back a
character encoding which was not listed in Accept-Charset. It's not
desirable, and this triggers a warning.

Why not a fail? This test covers external resources, which are
possibly outside the author's control. Some felt strongly that one
shouldn't FAIL (maybe only temporarily) on account of an external
resource. There are arguments both ways here, but that's why this is
considered a warning and not a failure.


>  If you want to support ISO-8859-1 in some way to make it easier for
> existing sites to server with the mobileOK label, ISO-8859-1 should simply
> be processed appropriately and added to the Accept-Charset header.

Sites are welcome to send back ISO-8859-1 whenever they like,
according to Accept-Charset or anything else. But as far as mobileOK
Basic Tests are concerned, we want to see the ability to return UTF-8
and test for that. That doesn't mean you always have to return UTF-8
to real devices.

To put it slightly differently, would you want to force Japanese sites
to return ISO-8859-1 to pass the tests?


>  Seventh, in section 3.18 POP_UPS, target attributes on links with values
> "_self", "_parent", or "_top" are accepted. All of these should FAIL,
> however, since their presence does not make sense (and is a waste of
> bandwidth) considering the requirements put forth in 3.13 NO_FRAMES.

This is a good point. They're a small waste of bandwidth. I think
we'll have to go gather some input on this and see whether there's any
non-trivial use case for this. I believe we'd like to considering
issuing a warning here rather than a fail since this test really
concerns pop-ups and not frames, but let me say this is something I
think deserves more discussion before the final draft.

Thanks as always for this valuable input!

Sean
Received on Sunday, 10 June 2007 23:09:35 UTC

This archive was generated by hypermail 2.3.1 : Monday, 29 September 2014 09:38:45 UTC