Re: [Ltru] [psg.com #1061] eliminate (or proscribe)Private Use Tags

["Randy Presuhn" <randy_presuhn at mindspring.com>]

Hi -

> From: "Mark Davis" <mark.davis at jtcsv.com>
> To: "John.Cowan" <jcowan at reutershealth.com>; "Randy Presuhn" <randy_presuhn at mindspring.com>
> Cc: <ltru at ietf.org>
> Sent: Friday, July 08, 2005 5:25 PM
> Subject: Re: [Ltru] [psg.com #1061] eliminate (or proscribe)Private Use Tags
>
> We can't say:
>
> >> They MUST NOT be distributed beyond the scope
> > >   of the relevant agreements.
>
> since people doing the distribution may not know what the scope is.

That's the point of using an RFC 2119 "MUST NOT".  It means "things
won't work if you do this".

> >> Subtags intended for wider
> > >   distribution MUST be registered.
>
> This is not actionable. wider than what? If I am using a protocol that
> transports language tags, is it incumbent upon me to examine the meaning of
> all of them? I think not.

No.  Again, this is an RFC 2119 "MUST".  It means, "in order for things
to work correctly , you have to do this".  It is not imposing a requirement
on the things that shovel tags around, just on the entity (which may be a human)
that decides how to tag something.

> The only thing we can really say is that:
> - don't use private use tags if you can at all avoid it
> - the only meaning they have is up to private agreement between parties
> - be aware if you do use them that they have no meaning -- or a different
> meaning! -- outside of the scope of a particular private agreement.

Here we're agreed.

> Randy's original is better:
>
> > (2) "Private-use subtags require private agreement between parties
> >     intending to use them. Use great caution if employing them in
> >     content or protocols intended for general use. Private-use subtags
> >     MUST conform to the format contraints specified in the ABNF.
> >     Private-use subtags are useless for information exchange without
> >     prior arrangement."
>
> Except that the "Private-use subtags MUST conform to the format constraints
> specified in the ABNF." is redundant. ALL subtags must conform to the format
> constraints specified in the ABNF. So I would just suggest the simpler

The reason I included the redundant element is because there indications
that someone plans to disregard the ABNF in their implementation.  Such
is their right, but I don't want them to have any excuses when things
don't work correctly.

> (2) "Private-use subtags have no meaning outside of a private agreement
> between parties. They may also be given different meanings by different
> private agreements between those or other parties. Thus they SHOULD NOT be
> used wherever there is alternative, and they SHOULD NOT be used in content
> or protocols intended for general use.
...

I could also live with this, if it will allow us to put this item to rest,
though I'd prefer if the second "SHOULD NOT" were a "MUST NOT".

Randy




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