Discussion List Archives

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [ddlm-group] UTF-8 versus extended ASCII

Dear Nick,

   For work with python, people do do mapping codecs from national
and system-specific variants of symbols to the official symbols.
This is not so much a change in what is defined as one of the
many, many encodings people use.  This group has decided not to
flag particular encodings, so I would suggest it is best to be
consistently blind to all such commonly used variants of
delimiters and separators, and just specify the reverse solidus
and the quote marks as they are in the first 127 characters
of the ASCII code page.  This does cause a peculiar anomally in
Japan, where the reverse solidus is usually preempted as the Yen
symbol, but by now, I think everybody in Japan is used to that,
and I am sure they will do what they have always done -- work
with Shift-JIS or EUC-JP  when convenient, and convert for export.
For their editors they will very likely insert the comment to
specify the encoding, but while they are doing that, they will
not be working with CIF2, but something else.  I would suggest they
call it CIF2-JP.  My guess is there will also be CIF2-CN and
CIF2-KR.  People work with the tools they are used to.

   With luck, as Unicode use and support spreads, we should be down
to just seeing primarily UTF-8 and UTF-16 variants 5-10 years from now.

   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
                  yaya@dowling.edu
=====================================================

On Tue, 10 Nov 2009, Nick Spadaccini wrote:

>
> Thanks, Herb. That was what I thought from what I could decipher of the W3C
> documentation, though I didn't appreciate the requirement to handle UTF-16
> also.
>
> But for the record we have been talking about delimiters and other special
> token characters and we are talking about the ASCII set of those characters
> aren't we? When I say \  (reverse solidus, RS) has special significance I am
> writing my parser to look for 0x5c, not the other possible reverse solidi(?)
> such as 0xEF 0xB9 0xA8 (small RS) or 0xEF 0xBC 0xBC (fullwidth RS). Same for
> quotes, double quotes etc.
>
> On 10/11/09 8:16 PM, "Herbert J. Bernstein" <yaya@bernstein-plus-sons.com>
> wrote:
>
>> Dear Colleagues,
>>    The basic answer is, yes, XML does accept much more than the ASCII
>> characters in its tags.  XML explicitly requires all proccessors of XML to
>> be able to handle boht UTF-8 and UTF-16, but restricts itself to the
>> following subset:
>>      #x9
>>      #xA
>>      #xD
>>      #x20-#xD7FF
>>      #xE000-#xFFFD
>>      #x10000-#x10FFFF
>>
>>
>>      #x100
>> =========
>> and "Document authors are encourage to avoif 'compatibility charcaters' "
>> and certain control characters or permanently undefined Unicode
>> characters.
>>
>> The whitespace characters are defined as space, carriage return, line feed
>> or the horizontal tab, but discourages explicit use of carriage return.
>> They are required to be removed or replaced by new-line before processing.
>>
>> Names may being with
>>      :
>>      A-Z
>>      _
>>      a-z
>>      #xC0-#xD6
>>      #xD8-#xF6
>>      #xF8-#x2FF
>>      #x370-#x37D
>>      #x37F-#x1FFF
>>      #x200C-#x200D
>>      #x2070-#x218F
>>      #x2C00-#x2FEF
>>      #x3001-#xD7FF
>>      #xF900-#xFDCF
>>      #xFDF0-#xFFFD
>>      #x10000-#xEFFFF
>>
>> and may continue with those plus
>>      -
>>      .
>>      0-9
>>      #xB7
>>      #x0300-#x036F
>>      #x203F-#x2040
>>
>> Does that answer the question?  There is more.
>>
>>    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
>>                   yaya@dowling.edu
>> =====================================================
>>
>> On Tue, 10 Nov 2009, Nick Spadaccini wrote:
>>
>>> I agree with James on this one. It is specified as UTF-8, so that is what
>>> you expect. Most of the files will be pure ASCII, as they are now, but over
>>> time that will change. If we say it can be extended ASCII, which is ALMOST
>>> (but not) the same as UTF-8 then I can only see confusion with users.
>>>
>>> I was discussing the move to UTF-8 with Syd the other day. He posed a
>>> question, the answer for which I took for granted, but now I am wandering.
>>>
>>> The specification for STAR is broad so it will say encoding is UTF-8. But
>>> when it comes to specific instances like CIF are we thinking that the data
>>> names in the file will still be restricted to the ASCII subset of UTF-8? I
>>> must admit I have been thinking of UTF-8 in terms of the data values, not in
>>> terms of the data tags.
>>>
>>> I have been trying to work out if XML accepts UTF-8 characters in the
>>> strings that define start- and end-tags (the elements). It looks like they
>>> do but every example I have seen works with the ASCII character set.
>>>
>>> Anybody know the answer.
>>>
>>>
>>> On 6/11/09 11:31 PM, "Joe Krahn" <krahn@niehs.nih.gov> wrote:
>>>
>>>> Traditionally, non-ASCII characters are encoded as "extended" ASCII,
>>>> using character codes 128-255. UTF-8 gained broad support because it
>>>> still fits this design, even though it encodes many more non-ASCII
>>>> characters.
>>>>
>>>> My suggestion is to define the low-level STAR2/CIF2 syntax as allowing
>>>> characters 128-255, but not specifically declaring UTF-8 encoding. It is
>>>> almost the same, but has a few potential advantages.
>>>>
>>>> First, it becomes a bit more sensible for the DDL to declare where UTF-8
>>>> is allowed, rather than excluding it from all of the other strings. I
>>>> assume that UTF-8 is intended mainly for publication-oriented formatted
>>>> text, but the numerous label strings will remain ASCII. If not, it still
>>>> follows the original STAR/CIF idea where the exact details of string
>>>> encoding is left to the DDL.
>>>>
>>>> Second, generic 8-bit extended ASCII would make it easier to efficiently
>>>> encode binary data, with 7-bits of raw binary data per byte. It has half
>>>> the overhead of Base64, and does not require mapping characters in a
>>>> look-up table. It is not as efficient as embedding binary in UCS-2, but
>>>> it also does not have the UCS-2 overhead for all of the non-binary CIF
>>>> files.
>>>>
>>>> The advantage of UCS-2 is that they easily fit into short fixed-length
>>>> strings, and are much more efficient at manipulating sub-strings. That
>>>> is why Java and the MS-Windows kernel use UCS-2. UTF-8 is more efficient
>>>> for storage, which is one reason MS-Windows does not default to UCS-2
>>>> for text files. Therefore, in my opinion, UTF-8 is better suited to an
>>>> archival format. However, UCS-2 might really be a better choice for
>>>> mostly-binary CIF files. It would be nice for UCS-2 CIF beginning with
>>>> the BOM encoding mark to also be a valid CIF alternative, instead of
>>>> just a hacked pseudo-CIF.
>>>>
>>>> If CIF still wants to go with global UTF-8 encoding, maybe the low-level
>>>> STAR syntax can be updated to define a more generic encoding. Herbert
>>>> mentioned that using "not exactly CIF" often is useful to get work done,
>>>> when the strict CIF format gets in the way. It would be nice if these
>>>> sorts of files could at least stick to STAR syntax to avoid running into
>>>> incompatibilities.
>>>>
>>>> OTOH, I am much more picky about proper syntax standards than most
>>>> people. Maybe this group is happy to declare standard CIF as UTF-8, and
>>>> leave any alternative forms as a customised, non-standard CIF.
>>>>
>>>> Joe Krahn
>>>> _______________________________________________
>>>> ddlm-group mailing list
>>>> ddlm-group@iucr.org
>>>> http://scripts.iucr.org/mailman/listinfo/ddlm-group
>>>
>>> cheers
>>>
>>> Nick
>>>
>>> --------------------------------
>>> Associate Professor N. Spadaccini, PhD
>>> School of Computer Science & Software Engineering
>>>
>>> The University of Western Australia    t: +61 (0)8 6488 3452
>>> 35 Stirling Highway                    f: +61 (0)8 6488 1089
>>> CRAWLEY, Perth,  WA  6009 AUSTRALIA   w3: www.csse.uwa.edu.au/~nick
>>> MBDP  M002
>>>
>>> CRICOS Provider Code: 00126G
>>>
>>> e: Nick.Spadaccini@uwa.edu.au
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> ddlm-group mailing list
>>> ddlm-group@iucr.org
>>> http://scripts.iucr.org/mailman/listinfo/ddlm-group
>>>
>
> cheers
>
> Nick
>
> --------------------------------
> Associate Professor N. Spadaccini, PhD
> School of Computer Science & Software Engineering
>
> The University of Western Australia    t: +61 (0)8 6488 3452
> 35 Stirling Highway                    f: +61 (0)8 6488 1089
> CRAWLEY, Perth,  WA  6009 AUSTRALIA   w3: www.csse.uwa.edu.au/~nick
> MBDP  M002
>
> CRICOS Provider Code: 00126G
>
> e: Nick.Spadaccini@uwa.edu.au
>
>
>
>
> _______________________________________________
> ddlm-group mailing list
> ddlm-group@iucr.org
> http://scripts.iucr.org/mailman/listinfo/ddlm-group
>
_______________________________________________
ddlm-group mailing list
ddlm-group@iucr.org
http://scripts.iucr.org/mailman/listinfo/ddlm-group

Reply to: [list | sender only]
International Union of Crystallography

Scientific Union Member of the International Science Council (admitted 1947). Member of CODATA, the ISC Committee on Data. Partner with UNESCO, the United Nations Educational, Scientific and Cultural Organization in the International Year of Crystallography 2014.

International Science Council Scientific Freedom Policy

The IUCr observes the basic policy of non-discrimination and affirms the right and freedom of scientists to associate in international scientific activity without regard to such factors as ethnic origin, religion, citizenship, language, political stance, gender, sex or age, in accordance with the Statutes of the International Council for Science.

Useful links