[Mpi-forum] Reserved MPI_ prefix & namespace in C and Fortran

William Gropp wgropp at illinois.edu
Sun Aug 26 12:37:43 CDT 2012

Thanks - fixing the must -> shall (like the illegal -> invalid) is something for MPI-next.  There are currently are large number of "must"s in the document.


William Gropp
Director, Parallel Computing Institute
Deputy Director for Research
Institute for Advanced Computing Applications and Technologies
Paul and Cynthia Saylor Professor of Computer Science
University of Illinois Urbana-Champaign

On Aug 26, 2012, at 11:47 AM, N.M. Maclaren wrote:

> On Aug 26 2012, Rolf Rabenseifner wrote:
>> About 1.: Yes, agreed. Always must and should are used as
>> synonyms in the scope of standards. To use the same
>> words in both sentences is clarifying that there is
>> no relevant difference in the meaning.
> Sorry, but definitely not in ISO standards!  From ISO
> Directives Part 2:
> Table H.1 - Requirement
> Verbal form       Equivalent expressions
> shall             is to
>                 is required to
>                 it is required that
>                 has to
>                 only ... is permitted
>                 it is necessary
> shall not         is not allowed [permitted] [acceptable] [permissible]
>                 is required to be not
>                 is required that ... be not
>                 is not to be
> Do not use "must" as an alternative for "shall". (This will avoid any
> confusion between the requirements of a document and external statutory
> obligations.)  Do not use "may not" instead of "shall not" to express a
> prohibition.
> Table H.2 - Recommendation
> Verbal form        Equivalent expressions
> should             it is recommended that
>                  ought to
> should not         it is not recommended that
>                  ought not to
> [End of extract]
> However, in non-ISO standards (and fairly often even in them!, "must"
> is used as a synonym for "shall".  It is definitely never a synonym
> for "should".
> Regards,
> Nick Maclaren.
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