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Re: [ddlm-group] Revisiting list delimiters

Dear James,

   I think your productions are fine and support them -- good idea.

   Inasmuch as we are not working from a reference implementation,
I would suggest we fill in as much detail as possible now on
the boundary cases to avoid future confusion.  I would suggest:

   <whitespace> does allow inclusion of comments, which is the
normal interpretation.

   and that the production

   <listdatavalue> = {<list>|<string>}<whitespace>*

means exactly what it says, which would mean that [,,] is
valid syntactically.  Rather than make that into a syntax
error as you said in your first text, I would suggest
keeping the parse simple and consistent and just giving
that one of the obvious meanings using either null data
values or empty strings (which I would suggest for
CIF2 simply be equivalent), so that [,,] would have the
same meaning as [.,.,.] or ["","",""] or ['','',''].

   That does no mean I recommend writing [,,] as good style,
but it has always been the case that CIF has accepted a lot
of strange ways of doing CIFS as valid for read and has
had good recommendatons for writing so that the result
is "clean" for people to read.

   Regards,
     Herbert


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

                  +1-631-244-3035
                  [email protected]
=====================================================

On Thu, 7 Apr 2011, James Hester wrote:

> Dear All,
>
> I apologise for the lack of detail in my introductory posting. If
> there is to be no quick agreement on the following, more formal,
> proposal, then I am happy to withdraw the proposal completely and we
> will continue on our previously agreed path.
>
> Note that I see no value in picking over Nick et. al's code as that
> code is not the final arbiter of every detail of what is or isn't in
> the standard - I was simply pointing out that it would be less work to
> fix the code to conform to the new standard if we don't deviate too
> far from the original.
>
> Here is my formal proposal: that a list be described by the following
> productions:
>
> <list> = '[' <whitespace>* {<listdatavalue> {<comma or
> whitespace><listdatavalue>}*}* ']'
> <listdatavalue> = {<list>|<string>}<whitespace>*
>
>
> On Wed, Apr 6, 2011 at 9:14 PM, Herbert J. Bernstein
> <[email protected]> wrote:
>> 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.
>>
>> � Regards,
>> � � Herbert
>> =====================================================
>> �Herbert J. Bernstein, Professor of Computer Science
>> � �Dowling College, Kramer Science Center, KSC 121
>> � � � � Idle Hour Blvd, Oakdale, NY, 11769
>>
>> � � � � � � � � �+1-631-244-3035
>> � � � � � � � � �[email protected]
>> =====================================================
>>
>> 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.
>>> --
>>> T +61 (02) 9717 9907
>>> F +61 (02) 9717 3145
>>> M +61 (04) 0249 4148
>>> _______________________________________________
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>>>
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>
>
>
> -- 
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> F +61 (02) 9717 3145
> M +61 (04) 0249 4148
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