Standard uncertainties (SU) in the DDLm dictionary

• Subject: Standard uncertainties (SU) in the DDLm dictionary
• From: Antanas Vaitkus <antanas.vaitkus90@xxxxxxxxx>
• Date: Wed, 12 Apr 2017 12:44:43 +0300
• DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025;h=mime-version:from:date:message-id:subject:to;bh=yjDsghmjwLYBJKujaKIhZoTbP+apAmQ/3dvm/V+DKPM=;b=LWr/I0kZnRAJGUeyT7YVzcCsbtfqIwCFcd/BqYtWJ2wQVSO2CtwmhAgFptOVNFBSmxWqFqAb6o7J734anJklQFRWXFLjYa9jatafge2NQ8d0QHnXzvuF6zxzC6ZK2/2REyFhP3KvCmBq0CJUc2GU7TYRHqAjVkyJLtpiYaQHZv8kWoWXnP9LJh8lj2bK59lR/V6eViyUaImtv0SrOtBUrM7IUXdFr7+3bffu1hZwJgh/q1wW531wAV/wsVtOO0RQUVaMep003wIJkDxYi0Y43lp8k0YnoL48XWIG5RHg+xlyqxYEQKPAScwq+YsMNB3CD0rFvsoB0I4dWiCsA0bIrg==

Hello,

I have several question about the way standard uncertainties should be specified to conform to the new DDLm dictionary. The definition of the "Measurand" enumerator value in the _type.purpose save block states that:
  This value must be accompanied by its standard uncertainty
   (SU) value, expressed either as:
    1) appended integers, in parentheses (), at the
         precision of the trailing digits,       or
    2) a separately defined item with the same name as the
         measurand item but with an additional suffix '_su'.

Several question arise from this definition:

1) Can the ways of expressing SU be used interchangeably?

For example, if the have a separately defined data item with the '_su' suffix in the dictionary, is it still allowed to specify the standard uncertainty using the parentheses ()? Consider the following situation:

If we have the following definitions in the dictionary that the CIF file conforms to:

    _measured_value

    _measured_value_su

Can we write the following in a valid CIF file:

    _measured_value   3.14(42)

Or is is strictly:
    _measured_value        3.14

    _measured_value_su 0.42

2) Does one way of expressing SU values have precedence over the other?

For example, If we have a CIF file with SU specified using both, the parenthesis () and the separate data item with differing values, should one of them be considered the preferred one?

_______________________________________________
cif-developers mailing list
cif-developers@iucr.org
http://mailman.iucr.org/cgi-bin/mailman/listinfo/cif-developers