DOCBOOK-APPS: autoidx.xsl

Hi,
in the autoidx.xsl stylesheet there are two entities defined:

<!ENTITY lowercase "'abcdefghijklmnopqrstuvwxyz'">
<!ENTITY uppercase "'ABCDEFGHIJKLMNOPQRSTUVWXYZ'">

Can some one explain me the reasoning behind why the "<l:gentext
key="lowercase.alpha"> and <l:gentext key="uppercase.alpha"> form
common/XYZ.xsl are not used ?


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Togan Muftuoglu