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Re: Comments on Pflugrath's comments

• To: Multiple recipients of list <imgcif-l@bnl.gov>
• Subject: Re: Comments on Pflugrath's comments
• From: Peter Keller <bsspak@bath.ac.uk>
• Date: Thu, 13 Jun 1996 13:16:41 -0400 (EDT)

I haven't really had the time to go through a lot of the recent stuff in
detail, but there are a couple of points arising from David's comments:

> The restriction of data names to 32 characters is also a cif rule (there 
> is no restriction in the STAR definition).  There have been a number of 
> requests to relax this rule and this may happen for some of the 
> dictionaries currently being written.  The problem with relaxing a rule 
> of this kind is that existing software may be written only to look at the 
> first 32 characters of the name.  There are a number of implications 
> that need to be considered before this rule can be abandoned.

This has already happened - the longest names in mmCIF are in the
STRUCT_SHEET_HBOND category, e.g.
_struct_sheet_hbond.range_1_beg_label_atom_id. If I have searched
correctly, there are 260 names in mmCIF which are 33 characters or longer,
including some in the DIFFRN_REFLECTIONS category. As far as I know, the
only current restriction on the length of data names is the CIF 80
characters to a line rule.

(For those of you, who haven't seen mmCIF, point your web browsers at
http://ndbserver.rutgers.edu/mmcif/index.html or at
http://www.ebi.ac.uk/NDB/mmcif/ ).

> The rule about having only one occurence of a dataname in a given datablock 
> is required so that one knows where the datavalue is to be stored.  If 
> multiple occurences of a dataname were allowed, the corresponding 
> datavalues would have to be stored in different parts of the memory, but 
> how would the program know where to store them?  Would it overwrite the 

[snip]

There is another very fundemental point about this which must be
understood - STAR says that the scope of data within a data block is
limited to that data block. If anything needs to be applied to several
data blocks, a global block must be used. BUT, CIF does not allow STAR
global blocks, so each data block in a CIF must be totally self-contained,
and independent of any other data blocks in the same file.

Cheers,
Peter.

========================================================================
Peter Keller.            \ 
Dept. of Biology and      \       "...nothing works, but
    Biochemistry,          \       everything survives...." 
University of Bath,         \ 
Bath, BA2 7AY, UK.           \        --- Carlos Fuentes
------------------------------\-----------------------------------------
Tel. (+44/0)1225 826826 x 4302 | Email: P.A.Keller@bath.ac.uk (Internet)
Fax. (+44/0)1225 826449        |   P.A.Keller%bath.ac.uk@UKACRL (BITNET)
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