The extension of Is_Basic to unicode (about AI12-0260-1)

[ytomino <aghia05@gmail.com>]

AI12-0260-1/04 Functions Is_Basic and To_Basic in Wide_Characters.Handling
http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ai12s/ai12-0260-1.txt?rev=1.5&raw=N

...Has already been formally adopted into RM? (status is "Amendment")

I found inconsistency between existing Characters.Handling.Is_Basic and new Wide_Characters.Handling.Is_Basic.

Characters.Handling.Is_Basic in RM:

   True if Item is a basic letter. A basic letter is a character that is in one of the ranges 'A'..'Z' and 'a'..'z', or that is one of the following: 'Æ', 'æ', 'Ð', 'ð', 'Þ', 'þ', or 'ß'.

Characters.H.Is_Basic includes only alphabet, not include other symbols.
Is_Basic ('+') = False.

Wide_Characters.Handling.Is_Basic in AI:

  Returns True if the Wide_Character designated by Item has no Decomposition Mapping in the code charts of ISO/IEC 10646:2017; otherwise returns False. 
  
Wide_Characters.H.Is_Basic includes all un-decomposable characters, called as "base character" in Unicode world. It include the symbols.
Is_Basic ('+') = True.

Perhaps, Is_Basic must be defined as the intersection of the set of base characters *and the set of letters* (categorized as 'Ll', 'Lu', 'Lt', 'Lm', 'Lo'... in Unicode Character Database).

Thanks.