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Re: Specifying values 'less than something' in CIFs?

• To: "Discussion list of the IUCr Committee for the Maintenance of the CIF Standard (COMCIFS)" <comcifs@iucr.org>
• Subject: Re: Specifying values 'less than something' in CIFs?
• From: Saulius Grazulis <grazulis@ibt.lt>
• Date: Sun, 29 Apr 2012 15:25:44 +0300
• In-Reply-To: <4F9D2CAB.7060908@bernstein-plus-sons.com>
• Organization: IBT
• References: <4F9CF725.9030608@ibt.lt> <4F9CF8CA.3050003@ibt.lt><4F9D2CAB.7060908@bernstein-plus-sons.com>

Dear Herbert,

many thanks for the answer!

On 04/29/2012 02:57 PM, Herbert J. Bernstein wrote:
> 0.001 is a number. <0.001 is a statement about a range
> of numbers.  In CIF at the moment, there is already
> a notation for some ranges of numbers, 0.0005(5), for
> example, meaning 0.0005+/-0.0005, which may or may not
> be intended to convey the same information as <0.001.
> mmCIF deals with this complexity by explicitly making
> _esd tags.
> 
> The issue needs to be dealt with in database searches.
> Should a search for .0004 be satisfied by data given
> as 0.0005(5)?  Most people would agree.  Should a
> search for .0004 be satisfied by data given as <0.001?
> Many people would be less certain.   Perhaps it is time to
> revisit these conventions and settle on some extensions to the
> notation to make life easier for users in preserving essential
> metadata compactly while preserving the searchability of data
> that includes that metadata.

I agree with both of you comments. So, if I understand you correctly,
specifying _refine_ls_shift/su_mean <0.001 in a DDL1 CIF should be
correctly done as

_refine_ls_shift/su_mean_lt 0.001

This is easy to do, and easy to fix automatically.

Regards,
Salius

-- 
Dr. Saulius Gražulis
Institute of Biotechnology, Graiciuno 8
LT-02241 Vilnius, Lietuva (Lithuania)
fax: (+370-5)-2602116 / phone (office): (+370-5)-2602556
mobile: (+370-684)-49802, (+370-614)-36366
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