Default bidi ranges

[Martin J. Dürst]

I tried to find something like a normative description of the default 
bidi class of unassigned code points.

In UTR #9, it says 
(http://www.unicode.org/reports/tr9/tr9-23.html#Bidirectional_Character_Types):

Unassigned characters are given strong types in the algorithm. This is 
an explicit exception to the general Unicode conformance requirements 
with respect to unassigned characters. As characters become assigned in 
the future, these bidirectional types may change. For assignments to 
character types, see DerivedBidiClass.txt [DerivedBIDI] in the [UCD].

The DerivedBidiClass.txt file, as far as I understand, is mainly a 
condensation of bidi classes into character ranges (rather than giving 
them for each codepoint independently as in UnicodeData.txt). I.e. it 
can at any moment be derived automatically from UnicodeData.txt, and is 
as such not normative.

Why is it then that the default class assignments are only given in this 
file (unless I have overlooked something)? And why is it that they are 
only given in comments? I'm trying to create a program that takes all 
the bidi assignments (including default ones) and creates the data part 
of a bidi algorithm implementation, but I don't feel confident to code 
against stuff that's in comments. Any advice? Is it possible that this 
could be fixed (making it more normative, and putting it in a form 
that's easier to process automatically)?

Regards,   Martin.