recommend Accept in preference to User-Agent to determine formats

Regarding...

"To determine what formats a device supports, Web sites may use any
combination of device profile information such as the HTTP User-Agent
header, HTTP Accept headers and UAProf."
 -- http://www.w3.org/TR/mobile-bp/ (2 November 2006)

The HTTP accept header is specifically designed for this purpose;
web sites SHOULD use it.

It's OK to say that they MAY use other stuff, but it doesn't
make sense to say that User-Agent is just as good as Accept
for figuring out what format the client wants.

I suggest:

  To determine what formats a device supports, Web sites should
  use the HTTP Accept header field; sites may use
  other information from the device (e.g. User-Agent, UAProf).


Some related, but more minor points:

"Some issues that have been noted by the BPWG in this context are:" is
wordy and refers to the BPWG, which is transient and
only tangentially relevant. Just strike that sentence and leave:

  There are problems with using any one approach to the exclusion
  of the others:


It's not clear to me why "User agent headers do not always
uniquely identify the device" is an issue. It's not necessary
to uniquely identify the device to figure out what formats
to use.

And in what way is it a problem that "Some operator gateways
supplement the accept headers to include formats that they adapt"?
That's a feature, not a problem.

You could usefully elaborate "Some devices do not supply accept
headers". The HTTP spec says "If no Accept header field is present,
then it is assumed that the client accepts all media types." So
I suggest you say:

  Some devices have unstated expectations about formats;
  they do not supply accept headers, but neither do they
  accept all formats.

Putting "UAProf information may not be available or may be
incomplete" in the same list as protocol errors such
as "Some devices mis-state their capabilities" seems misleading.
I can't think of a specific suggested fix, though.



-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E

Received on Wednesday, 29 November 2006 09:29:12 UTC