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Re: [ddlm-group] Revisiting list delimiters

A brief response to this, as I try to clear my desk for a week away.
I had little to say regarding the technical aspects of this choice
last time, and I have nothing to add - so long as the result is
clearly documented and addresses the edge cases, either is acceptable.

My routine application of Ockham's razor argues in favour of a single
delimiter rather than two, although I accept that the adoption of one
"unnecessary" entity in this case would be less of an overhead than
the multiplicity of "unnecessary" escapes that would follow the adoption
of the Python specification for triple-quoted strings. And I see
some merits in the argument Herbert put forward that one could
fashion some "CIF 1.5" stratagems for handling the new list structures
within the CIF 1 syntax model. But such a hack in turn conflicts with the
"maximal disruption" principle that would clearly and cleanly differentiate
between the two models.

If a formal vote is required during my absence, you may take it that
I would still abstain.


On Wed, Apr 06, 2011 at 04:36:21PM +1000, James Hester wrote:
> Dear DDLm-group,
> In the process of preparing for a vote on accepting the DDLm
> dictionary, I have come to the conclusion that we need to revisit the
> question of the separator character for lists.  This is because the
> only fully-functional software for processing DDLm domain dictionaries
> (Nick, Syd and Ian's demonstration software) expects a comma
> separator, and my understanding is that Syd and Nick (now) are
> strongly in favour of sticking with comma as the list separator for
> STAR2.  Furthermore, other non-CIF domains collaborating with Nick and
> Syd are already using comma as a list separator in STAR2 data files.
> Additionally, I've formed the view that a comma is a useful visual aid for
> distinguishing looped items and listed items.
> I've reviewed our previous discussion starting at message:
> http://www.iucr.org/__data/iucr/lists/ddlm-group/msg00338.html and
> culminating in a tally at
> http://www.iucr.org/__data/iucr/lists/ddlm-group/msg00406.html (with a
> late vote after this from John W. for spaces only).  It seems that the
> strongest preferences expressed were from Herb (for comma and space)
> and from John W (for space only in order to avoid mixed-delimiter
> strings).
> I would therefore like to propose that we switch to allowing comma
> *or* space as list item delimiters.  This will considerably simplify
> the work needed to adapt the current DDLm/dREL software and
> documentation.  I am also open to switching back to comma only, but think
> that that might meet with some resistance.
> I apologise for reopening this old discussion, but it looks like
> reintroducing commas will produce the best practical outcome.  Note
> that I would propose keeping the behaviour that was generally accepted
> in the previous discussion, i.e.
> * two commas without an intervening value is a syntax error, as is a
> trailing comma
> * lists may use a combination of comma and whitespace separation
> (although one might expect that to be vanishingly rare in practice)
> but this should be discouraged.
> If I hear no strong dissenting voices, I will produce some draft text
> for your comment
> then edit it into the draft standard when it next comes before COMCIFS.
> Once we have resolved this issue, I will edit the draft DDL
> specification to take into
> account variations in CIF2 syntax from that assumed for the original
> specification, then
> present it for your vote.
> James.
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