Re: should guidelines say something about NOT using IMPLIED?

["David T. Perkins" <dperkins@dsperkins.com>]

HI,

The original reason why the IMPLIED qualifier was added was to deal
with the problem was that the encoding of string indices was
incomplete, and thus, some agent/managers encoded strings with
a leading length and some didn't (when the string was varying
in length). The IMPLIED was added to document the implementations.
Now, after it was added, some people saw that it "solved" the
"Fred - Barney" problem. (The "fred - barney" problem is that
"fred" sorts before "barney" when prefixed by a length, but
afterwards if the sorting is alphabetical.) The solution,
as RandyP points out below, is not complete. But those people
that liked strings and did management with MIB browers,
did lots of MIB designs with strings as indices using the
IMPLIED qualifier. (end of history revisited).

At 01:42 PM 2/17/2003 -0800, Randy Presuhn wrote:
>Hi -
>
>> From: "C. M. Heard" <heard@pobox.com>
>> To: "Mreview (E-mail)" <mreview@ops.ietf.org>
>> Sent: Sunday, February 16, 2003 7:16 PM
>> Subject: Re: should guidelines say something about NOT using IMPLIED?
>>
>
>> On Sun, 16 Feb 2003, Randy Presuhn wrote:
>> > ...
>> > > +      have to be replicated.  Designers who are nonetheless tempted to
>> > > +      use IMPLIED because it results in a "natural" sort order for text
>> > > +      string index objects are urged to remember that this is at best
>> > > +      true only for US-ASCII strings and isn't true at all for general
>> > > +      UTF-8 strings.
>> > ...
>> >
>> > It can fail miserably for ASCII if the strings are mixed case or
>> > the language isn't English.  (Consider the traditional sorting rules
>> > for Spanish.)  I think "at best" is being rather generous.
>>
>> So, what should I say instead?
>....
>
>Perhaps "Designers tempted to use IMPLIED should consider that the
>resulting sort order rarely meets user expectations, particularly if the
>strings include both upper and lower-case letters, and does not take
>the user language or locale into account."
>
>Randy
Regards,
/david t. perkins