The IPP working group has chosen to base the IPP project (partly)
on ISO 10175 - DPA (Document Printing Application). In order for
"text" strings specified in IPP to be transferred to and from
strings in DPA implementations (there are a number), it is helpful
to observe the DPA limitation to ISO 10646 Level 2.
Perhaps this was an unfortunate choice in the ISO DPA standard.
The rationale was in order to help support correct comparison
operations for string attributes.
Certainly, access to the full repertoire of ISO 10646 Level 3
is highly desirable (for the reasons you stated in your note,
below).
But if IPP/1.0 is to be rapidly adopted and deployed by the
printing industry vendors, it must avoid unreasonable implementation
costs for embedded systems.
I recently read the MIME media-type registration for UTF-8 and
it seemed somewhat ambiguous about which level of ISO 10646
is mandatory.
The IPP working group has approximately three (3) weeks left
to finish their Model and Semantics spec and Protocol spec
and advance them to the IESG (per a recent note from Keith
Moore, one of our IETF Applications Area Directors), if the
IPP/1.0 specs are to be adopted within calendar 1997. There
is a very real urgency about completing IPP/1.o specs soon.
Otherwise, it is probable that single-vendor or small
consortium implementations of something "similar" to IPP,
but NOT interoperable. And the "window of opportunity"
to solve the problem of a robust replacement for RFC 1179
will have passed.
Regards,
- Ira McDonald (outside consultant at Xerox)
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Date: Tue, 14 Oct 1997 06:51:59 PDT
To: Tom Hastings <hastings@cp10.es.xerox.com>
From: Francois Yergeau <yergeau@alis.com>
Subject: IPP> Re: MOD - Comment on RFC 2044: need to specify the ISO 10646
conformance level
Cc: Harald.T.Alvestrand@uninett.no, Keith Moore <moore@cs.utk.edu>,
ipp@pwg.org
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Status: R
=C0 21:52 08/10/97 PDT, Tom Hastings a =E9crit :
>For the purposed of Internet Protocols, we suspect that level 2 is
sufficient.
>But the UTF-8 definition in RFC 2144 is silent on this matter. We suggest
>that
>a refision to RFC 2144 be issues that indicates that utf-8 means just
level 2.
A restriction to level 2, which excludes most combining characters, would
severely restrict the expressive power of ISO 10646, and in consequence the
ability of the protocols that use it (in the UTF-8 form) to represent the
textual content that they need to represent for truly world-wide operation.
IMHO, such a restriction is too serious to be entertained solely on the
basis of "we suspect that level 2 is sufficient." ISO has not found it
sufficient, it has level 3; Unicode has *only* level 3. And I think the
purposes of Internet protocols (at least those that carry text) are the
same as the purposes underlying ISO 10646 and Unicode: to enable
communication in all the world's languages.
>Alternatively, register a new value, say, 'utf-8-level-2'.
There is actually a revision of RFC 2044 underway. The latest draft
(ftp://ds.internic.net/internet-drafts/draft-yergeau-utf8-rev-01.txt) has a
discussion of version-specific labels, which you may find relevant to your
proposal of a level-specific label. Please take a look, and come back with
your proposal -- preferably to the ietf-charset list, as suggested by
Harald -- if you still think it is appropriate.
Regards,
--=20
Fran=E7ois Yergeau <yergeau@alis.com>
Alis Technologies inc., Montr=E9al
T=E9l : +1 (514) 747-2547
Fax : +1 (514) 747-2561