(This dates from July 20, 2009, when the CONTEXTO issue was still open. It is now moot.)
I believe that none of the current CONTEXTO characters are really required to be CONTEXTO, and all should be simply PVALID.
Here are my recommendations in detail:
The rule on HYPHEN is unnecessary, since it is a requirement of the DNS system anyway; this is completely redundant. So remove from Tables:
Appendix A.1. HYPHEN-MINUS
Must not appear at the beginning or end of a label.
If FirstChar .eq. cp Then False;
If LastChar .eq. cp Then False;
Note that in Protocol we have:
The Unicode string MUST NOT contain "--" (two consecutive hyphens) in
The corresponding Lookup restriction is missing from Protocol and should be added.
the third and fourth character positions.
B. ARABIC-INDIC DIGITS
The rule on these overlaps with Bidi, and would be simpler and more appropriately moved there, since these are all only of concern with Bidi processing. So remove:
And change BIDI from:
5. If an EN is present, no AN may be present, and vice versa.
If an EN is present, no AN or EXTENDED ARABIC-INDIC digit
(U+0660..U+0669) may be present. If an AN is present, no EXTENDED
ARABIC-INDIC digit (U+0660..U+0669) may be present.
C. Other CONTEXTO
Remove the other CONTEXTO cases. These consist of only the following
6 characters, and there is no particular problem with making them all
simply PVALID in the Exceptions table.
|but different placement
||GREEK LOWER NUMERAL SIGN
|but , is illegal anyway
||HEBREW PUNCTUATION GERESH
|but ' is illegal anyway
||HEBREW PUNCTUATION GERSHAYIM
|but " is illegal anyway
||KATAKANA MIDDLE DOT
|but different placement, width
||COMBINING CYRILLIC TITLO
||unclear motivation; but no worse than other combining marks. If
there is any problem with that, just make it DISALLOWED in the Exception section; it is archaic anyway.