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Re: [ddlm-group] Revisiting list delimiters

Dear James,

   Before we settle this, I would suggest we all look
at Nick, Syd and Ian's demonstration software, so we
are all working from the same base.  Is there a
URL we can all go to to see a reference implementation
of STAR2, or should we be looking at the DDLm code
from 2006 and 2007 so see the handling of lists
referred to.  I am particularly concerned about the
handling of boundary cases, such as trailing commas
and empty pairs of commas, and embedded comments,
where actual code is very helpful in understanding
what is intended.

  Herbert J. Bernstein, Professor of Computer Science
    Dowling College, Kramer Science Center, KSC 121
         Idle Hour Blvd, Oakdale, NY, 11769


On Wed, 6 Apr 2011, 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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> F +61 (02) 9717 3145
> M +61 (04) 0249 4148
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