Subject: RFC 2534 list of ua-media and paper-size values

From: "Larry Masinter" <[email-masked]>
Date: Thu, 14 Oct 1999 19:25:32 PDT

HTML 4.0 (http://www.w3.org/TR/html40) contains a list of devices
("media") that is used for selection of style sheets. This list
of devices includes:

screen 	Intended for non-paged computer screens. 
tty 	       Intended for media using a fixed-pitch character grid,
              such as teletypes, terminals, or portable devices with
              limited display capabilities. 
tv            Intended for television-type devices (low resolution, color,
              limited scrollability). 
projection    Intended for projectors. 
handheld      Intended for handheld devices (small screen, monochrome,
              bitmapped graphics, limited bandwidth). 
print         Intended for paged, opaque material and for documents viewed
              on screen in print preview mode. 
braille       Intended for braille tactile feedback devices. 
aural         Intended for speech synthesizers. 
all           Suitable for all devices. 

which seems to overlap the various conceptual spaces of CONNEG
media featuresincluding RFC 2534's ua-media:

     screen           A refreshable display
     screen-paged     a refreshable display which cannot scroll
     stationery       Separately cut sheets of an opaque material
     transparency     Separately cut sheets of a transparent material
     envelope         Envelopes that can be used for conventional
                      mailing purposes
     envelope-plain   Envelopes that are not preprinted and have no
                      windows
     continuous       Continuously connected sheets of an opaque
                      material

I would guess that HTML 4.0 "print" == CONNEG "ua-media=stationery"
+ some kind of range (unspecified) of resolution & pix-x & pix-y.

HTML has no notion of "transparency" or "screen-paged" (except
maybe in combination with low resolution of "tv"), while CONNEG
has no value for "braille" or "aural".

IPP (RFC 2566) in Appendix C has a different set of "media", where
"media" includes size, and whether or not the paper is colored, etc.
It's a pretty lengthy list, so I won't reproduce it here.

Anyway, I think we might want to take another look at the list
of media values and update it, possibly providing for some other
mechanism for registering new values.

I'm convinced that the approach taken by conneg of handling
sizes separately from the nature of the medium is correct, but
that we might want to revisit the list of paper sizes & media
types to align IPP and CONNEG and HTML, possibly recycling
updating RFC 2534.

Part of this would be so that IPP might consider using 
CONNEG feature sets to talk about both capability and availability,
and that HTML and CCPP might use the same vocabulary.

Larry

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From: [email-masked] (Koen Holtman)
Date: Fri, 15 Oct 1999 18:10:54 +0200 (MET DST)

Larry Masinter:
[....]
>mechanism for registering new values.

In principle, the media feature tag framework is powerful enough to
allow for the co-existence of both the RFC 2534 ua-media vocabulary and
the HTML 4.0 vocabulary alongside each other.

In this particular case, however, I agree that merging them is an
appropriate way to go currently, as there are no deployed uses of the
ua-media tag (I know of) yet.

Transforming the ua-media value set into an open-ended set, to which
new values can be added at will in future even after some deployment,
is a much bigger step, and one that I would not want to take.  There
is a definite advantage to application and content authors in having a
small, stable set of values with a guarantee that, for example, a
value like 'screen' will not be superceded by 3 alternative other
values in future.

New kinds of distinctions, inside already registered ua-media
designations, are better handled by the introduction of completely new
tags.

>Larry

Koen.

---

From: [email-masked]
Date: Fri, 15 Oct 1999 13:24:55 -0700 (PDT)

Larry,
	I am certainly willing to look at the list and add new items
which seem necessary. I don't want to remove any item from the list
(archival availability being one of the things we're selling with
registered items), though we could update the registrations to note
parallel, preferred items.  I am not sure what changes to registration
process you are suggesting, though; can you clarify?
			best regards,
				 Ted Hardie

---

From: "Larry Masinter" <[email-masked]>
Date: Fri, 15 Oct 1999 14:28:28 PDT

Here's a cut at vocabulary alignment between HTML and RFC 2534.

HTML screen: arguably the same as RFC2534 screen
HTML tty: no analog; add this to RFC 2534
HTML tv: combines several media features. I suggest changing RFC 2534
         'screen-paged' to add "or which has limited scrolling capabilities"
         to "which cannot scroll", and then defining HTML tv as
         'screen-paged', color=full and some description of
         pix-x & pix-y
HTML projection: is this a kind of 'screen'? Or we should register it? 
HTML handheld: No media feature for "limited bandwidth"; maybe we need
         some feature to describe size in bytes, e.g., 'docsize<2000' ?
         otherwise (small screen, monochrome, bitmapped graphics)
         corresponds to ua-media=screen,pix-x<200,pix-y<200,color=binary
HTML print: sort of like 2534 stationery. In retrospect, I wonder about the
         RFC 2534 distinction with 'transparency', 'envelope', 
         'envelope-plain' is useful. I was trying to be compatible
         with the printer mib, but it's not really "ua-media".
         'continuous' might have been useful for fax if it really
         denoted 'roll paper', but the definition there says
         'continuously connected sheets of opaque material' which
         makes it sound like it's paged.

HTML braille, aural:  these aren't in RFC 2534, and probably should
         be.

If we add 'print', we could eliminate or deprecate 'stationery',
'envelope', 'envelope-plain', 'transparency' and 'continuous' in
favor of recognizing 'print', then the relationship with IPP is
clearer, since most of the IPP media types are a kind of 'print'.

Summary of changes to RFC 2534 UA-Media
    add 'tty'
    modify 'screen-paged' to note "or limited scroll capabilities"
    add 'projection'
    add 'print' as "any kind of printed material".
    deprecate 'continous', 'transparency', 'envelope', and 'envelope-plain';
      note that these are kinds of 'print'. Note that
      continuous rolls might be noted as 'print' with no pix-y limit.
    add 'braille' and 'aural' with the same definitions as in HTML 4.0.

For alignment with IPP, we'll need to update RFC 2534 paper sizes
(mainly adding values), add feature(s) for paper color(ed), and then
describe IPP media primarily as "print". Maybe 'continuous',
'transparency', 'envelope' and 'envelope-plain' are all parts
of some (new) paper-type feature.

---

From: Al Gilman <[email-masked]>
Date: Fri, 15 Oct 1999 23:33:53 -0500

>HTML projection: is this a kind of 'screen'? Or we should register it? 

Close match to screen-paged.  But note that for projection one uses larger
fonts, so projection is an issue in itself.  See also

<http://www.w3.org/TR/REC-CSS2/media.html#media-types>.