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Re: Some additional obscure questions...Forward Refs


1)Is support for forward references required in the MIB module language?
The answer is "OF COURSE".

2)Can a rule be made such that all OID values defined in a MIB
module are "under" the OID value specified in the MODULE-IDENTITY?
The answer is "OF COURSE NOT".

3)Could a new language be specified that doesn't allow forward references?
The answer is "OF COURSE".

This is really old stuff. REALLY OLD.

At 04:02 PM 2/3/2003 -0500, Bob Natale wrote:
>At 2/3/2003:03:35 PM, David T. Perkins wrote:
>Hi Dave,
>>I think you are trying to change the point,
>You're right -- in an attempt to learn something
>from you (and anyone else who cares to comment --
>so I've modified the Subject header to reflect the
>current focus.
>>which is that examples to demonstrate conformance are more powerful
>>when they check all aspects of the conformance instead of the trivial
>True...but examples which demonstrate arcane scenarios
>and/or non-standard/non-required features might contribute
>more to confusion than to elucidation.
>>Of course,
>>examples to "teach" about functionality would be written differently.
>>And examples to show common practice would be different.
>>On the forward reference issue....
>>First, forward references are a feature of ASN.1, and one that is
>>carried forward to the MIB module language.
>Where is the requirement in the SMI to support forward references?
>>(And yes, supporting or not supporting forward references makes a BIG
>>difference in MIB compiler design, including data structures and error
>>detection and reporting!)
>Yes, supporting fwd refs complicates those aspects significantly.
>Hence, one would want to be certain that doing so is required
>by the applicable standards.
>>Second, someone would have to do all the work to determine if
>>eliminating all forward references would create an undue hardship
>>on writing (and reading) MIB modules.
>Are you suggesting none of the MIBs with fwd refs can be
>compiled by any of the MIB compilers that don't support
>fwd refs?  Or, would you say that those MIBs can normally
>be compiled by such compilers with relatively modest editing
>to the MIB source file?  Answering "yes" to the first question
>seems impossible, given existence proofs.  Answering "yes" to
>the second question indicates clearly that fwd refs are not
>required in practice.
>>There is one place (not in the imports) that MIB compilers not
>>supporting forward references results in pretty ugly MIB module
>>specification. That is the OID value that is used for the value
>>of a MODULE-IDENTITY construct.
>Given some standard root starting point(s) -- which we have --
>there is no MODULE-IDENTITY value that could not be specified
>directly as a successor to an IMPORTed value, I believe.  Am
>I wrong about that?  Furthermore, IMHO, every MODULE-IDENTITY
>value *ought* to be so constructed...first as a matter of
>good design and second as a requirement (since I am currently
>unaware of the SMI requirement to support fwd refs).
>As I said, I suspect I'll learn something from this thread!
>(And thanks for taking the time.)
/david t. perkins