Re: [ubl-clsc] My additions to the Code List Design Requirements

["Anthony B. Coates" <abcoates@londonmarketsystems.com>]

** Reply to message from Alan.Stitzer@marsh.com on Wed, 14 Jan 2004 14:35:32
-0500

> [R19] A list of the values (codes) for a code list
> 
> The code list must contain at least three (3) valid values to be considered
> a code list.  If a code list contains only two values, it should be
> considered a "boolean".

I must admit, it is not uncommon for people to use a boolean value to represent
a choice between just two items.  In my opinion, it is often a mistake.  Many
choices between two items are not really boolean choices.  For example, suppose
sets of tea cups are available in white or blue.  You could map that choice
onto a boolean value, but when sets of red tea cups become available the next
year, rewriting your boolean code to account for the existence of 3 values
could be expensive.

When mapping to a boolean value, the issue is not just whether you have two
values.  Rather, you have to ask whether the two values you have are the only
two values that could ever be possible.  If not, then a boolean is the wrong
choice.  This is my guiding rule, anyway.

	Cheers,
		Tony.
====
Anthony B. Coates
London Market Systems Limited
33 Throgmorton Street, London, EC2N 2BR 
http://www.londonmarketsystems.com/
mailto:abcoates@londonmarketsystems.com
Mobile/Cell: +44 (79) 0543 9026
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