[vhdl-200x] Request for comment: renumbering VHDL LRM clauses

From: Peter Ashenden <peter_at_.....>
Date: Tue Jul 17 2007 - 22:36:21 PDT
Dear colleagues,

This is a request for comment on a proposal to renumber clauses of the VHDL
LRM to meet current IEEE style guidelines.

The IEEE rules have evolved during the lifetime of the VHDL standard, and
the standard is now not conformant. IEEE would like us to revise the
document to conform with the current style rules. That would result in
significant changes to the numbering of clauses and subclauses in the
document. (A more detailed description is below.) As a consequence, and
implementation that referred to LRM clause or subclause numbers (eg, in
error messages), would have to be revised, and would have to maintain
different references for different versions of the language.

The VHDL working group would appreciate comments from users and implementers
of the standard to determine the extent of the effect of renumbering. If
there is significant objection to renumbering, the working group could make
representations to IEEE to maintain the current numbering. If there is not
significant objection, then the technical editor could proceed to implement
the renumbering.

If you would like to comment, please reply to this message (NOT reply-all),
and I will collate responses. Please reply by 5pm Friday 27-Jul US-PDT.

Some further detail:

The current numbering of LRM clauses and subclauses has been maintained
largely unchanged since the original VHDL-87 standard. Explanatory
information was added in the VHDL-93 standard as Clause 0, in order not to
change the numbering of subsequent clauses. Additional subclauses were added
in VHDL-93 and -2000, but at the ends of clauses, so as not to perturb
exiting numbers. In VHDL-2006/D3.0, some subclauses were moved and others
inserted, but consequent renumbering is minimal, especially given the scope
of extensions.

Since the earlier version of the LRM were published, IEEE has evolved its
style guidelines covering what goes in a standard and where. Some or the
guidelines stem from requirements on ANSI and international standards. In
particular, IEEE standards are now required to have:

- an Overview as Clause 1 containing the Scope and Purpose, and NOT
  detailed discussions of the general technical content of the standard
- if normative references are used, they constitute Clause
- if definitions are required, they constitute Clause 3

Implementing these changes would result in Clause numbers changing.

The rules also require certain structure of clauses and subclauses. If a
clause contains subclauses, then there must not be text preceeding the first
subclause; that text should itself be in a subclause. Subclauses must be
similarly structured. These rules avoid a reference to, say, Clause 5, being
ambiguous (interpretable as just referring to the introductory text or
referring to the clause and all its subclauses). Application of these rules
would result in changes to subclause numbering within clauses.

Furthermore, each clause or subclause can contain at most one numbered list.
If more are required, the clause must be subdivided with each list in a
separate subclause. This ensures that a list item can be unambiguously cross
referenced by prefixing it with its containing subclause number.



Dr. Peter J. Ashenden         peter@ashenden.com.au
Ashenden Designs Pty. Ltd.    www.ashenden.com.au
PO Box 640                    VoIP: sip://0871270078@sip.internode.on.net
Stirling, SA 5152             Phone: +61 8 7127 0078
Australia                     Mobile: +61 414 70 9106

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Received on Tue Jul 17 22:36:38 2007

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