DISPLAY-HINT and our MIB review Guidelines

["Wijnen, Bert (Bert)" <bwijnen@lucent.com>]

MIB Doctors,

I am having a debate with Keith McCLoghrie on our 
guideline that suggests a DISPLAY-HINT  for a TC
is a good thing. 

I do not intend to keep this discussion ongoing, and I will 
let Keith have his way without a DISPLAY-HINT.

I just want you to be aware.

Thanks,
Bert 
----------------
The document in question is: draft-ietf-ips-fcmgmt-mib-05.txt

> > > ./FC-MGMT-MIB:62: [5] {type-without-format} warning: type 
> > `DomainIdOrZero' has no format specification
> >

> >   DomainIdOrZero ::= TEXTUAL-CONVENTION
> >       STATUS current
> >       DESCRIPTION
> >             "The Domain Id (of a FC switch), or zero if the no Domain Id
> >             has been assigned."
> >       SYNTAX  Integer32 (0..239)
> > 
> > > I think the warning is cause by the fact that there is no 
> > > DISPLAY-HINT.  Can you add those?
> > 
> > I can't because, as far as I know, there is no standard format for
> > displaying these.  Anyway, RFC 2579 says that DISPLAY-HINT is 
> > optional.
> > So, this is another bug in that compiler.  Why is the IETF's 
> > MIB review process relying upon a buggy compiler ??
> 
> OK, I asked "can you add those?" I did not say "you MUST add those".
> AS you note, they are optional. However the set of current MIB doctors
> have composed a set of guidelines for review, and document
>     draft-ietf-ops-mib-review-guidelines-02.txt
> represents the current guidelines and sect 4.6.3 recommends to add
> a DISPLAY HINT:
> 
>    4.6.3.  DISPLAY-HINT Clause
> 
>    The DISPLAY-HINT clause is used in a TC to provide a non-binding hint
>    to a management application as to how the value of an instance of an
>    object defined with the syntax in the TC might be displayed.  Its
>    presence is optional.
> 
>    Although management applications typically default to decimal format
>    ("d") for integer TCs which are not enumerations and to a hexadecimal
>    format ("1x:" or "1x " or "1x_") for octet string TCs when the
>    DISPLAY-HINT clause is absent, it should be noted that SMIv2 does not
>    actually specify any defaults.  MIB authors should be aware that a
>    clear hint is provided to applications only when the DISPLAY-HINT
>    clause is present.
> 
> So... Can you add one please.

I already answered: no because I don't know what the correct hint is.

> If nothing else, then use "d"

Why, if it might be wrong ??

Note that DISPLAY-HINT has always been a compromise between being
simple versus being powerful.  That is, DISPLAY-HINT was intentionally
kept simple even though its simplicity prevents it from being able to
represent complicated display formats.  Specifically, it's not possible
to express all display formats with DISPLAY-HINT, and thus, it makes
no sense for it to be required.  That's also why it's a "hint".

> If you disagree with the mib-review guideline. pls speak up on
> ietfmibs@ops.ietf.org list, so we can re-evaluate. This guidelines doc
> is on its way to become a BCP.

But I don't disagree, because as your quote says, with no ambiguity
possible:

    Its presence is optional. 
 
> The compiler by the way only generates a warning, not an error!
 
I'm confused.  Why do you even get a warning for omitting something which
is optional ?

Keith