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Re: [ddlm-group] Elide close quotes by doubling?

On 5/12/09 5:59 AM, "Joe Krahn" <krahn@niehs.nih.gov> wrote:

> OK, I agree that this can be revisited later. If CIF1-embedded quotes
> are invalid, then adding a repeat-quote elide will not interfere with
> any other syntax, so it does not have to be a concern in the initial
> CIF2 spec.

Actually it will interfere lexically in CIF2. You are suggesting "" to be
the same as an embedded ", however the first subsequent " after the
intialising ", terminates the delimited string. Hence "" won't work.

But on a wider issue you are simply revisiting the elide discussion of last
week(s). There is no great difference between a "" vs \", the reason we
couldn't ultimately agree is because of our inability to separate user
defined elides and CIF2 generated lexical elides. A CIF2 syntax issue that
is not a user issue should be handled by the parser for the user. Others see
it as a user issue for them to insert and delete "lexical" elides.

James and I see the latter approach as necessarily ambiguous and gave
several examples of how it would be ambiguous.

>From there we decided that in the end it would be much easier if users used
alternative delimiters.

> As for Simon's commen on avoiding the need for an elide, maybe he is
> including the possibility of containing anything within semicolon quotes
> if it is indented by at least one space to elide internal semicolon
> quotes. I would rather see a formal elide mechanism, but that is a good
> workaround.
> Joe
> Herbert J. Bernstein wrote:
>> Just for the record, we did _not_ agree " that there were enough
>> alternative data value delimiters to avoid the use of any eliding
>> mechanism,". What we agrees to was to stop arguing about how to
>> use a reverse solidus and to take all strings as is.  I am certain we
>> will eventually need some mechanisms to:
>>    deal with long lines
>>    deal with quoting of arbitrary text
>> But neither issue is worth holding up the use of methods as quickly
>> as possible.  We need to get something out that will allow dictionaries
>> to get written using methods and out into use.  The current CIF 2
>> specification is adequate to allow dictionaries to get written, and
>> to deal with a large subset of what is needed in data files.  I hope
>> we will continue this discussion _after_ getting CIF 2 with DDLm
>> out and in use to see what is appropriate to extend the  useful range
>> of data files.
>> =====================================================
>>   Herbert J. Bernstein, Professor of Computer Science
>>     Dowling College, Kramer Science Center, KSC 121
>>          Idle Hour Blvd, Oakdale, NY, 11769
>>                   +1-631-244-3035
>>                   yaya@dowling.edu
>> =====================================================
>> On Fri, 4 Dec 2009, SIMON WESTRIP wrote:
>>> Judging by the difficulties we had that eventually led to agreeing
>>> that there were enough alternative data value delimiters to avoid
>>> the use of any eliding mechanism (and thus returning all values as raw),
>>> I suspect that arguing for a different eliding mechanism will also be
>>> fruitless?
>>> I understand your view (Joe) about CSV, but we have to respect the
>>> legacy that is CIF, which is why we have a variety of delimiters.
>>> Otherwise, it could probably be argued that only one type of delimiter is
>>> necessary
>>> (say """")...
>>> Cheers
>>> alt
>>> Simon
>>> ____________________________________________________________________________
>>> From: Joe Krahn <krahn@niehs.nih.gov>
>>> To: Group finalising DDLm and associated dictionaries <ddlm-group@iucr.org>
>>> Sent: Friday, 4 December, 2009 18:03:03
>>> Subject: [ddlm-group] Elide close quotes by doubling?
>>> The reverse solidus (aka backslash) elide was dropped because it really
>>> does not work well to elide only the close quote. Now that close quotes
>>> are invalid when not followed by white space, it provides the
>>> opportunity to elide close quotes by a repeated close-quote sequence,
>>> similar to Fortran and CSV format. It is free of most of the
>>> repercussions of defining reverse-solidus as an escape character, and is
>>> only making use of a character sequence that would otherwise just be a
>>> syntax error.
>>> The caveat is that it could misinterpret valid CIF1 values. However, at
>>> least RCSB has done a good job of avoiding embedded quotes by picking
>>> alternate quoting types.
>>> There are workarounds for embedded quotes, even for CIF-within-CIF, so
>>> elides are not essential. However, I think this should be easy to
>>> implement, and free of the hassles generated by backslash escapes.
>>> Thanks,
>>> Joe Krahn
>>> _______________________________________________
>>> ddlm-group mailing list
>>> ddlm-group@iucr.org
>>> http://scripts.iucr.org/mailman/listinfo/ddlm-group
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