Julian Mehnle wrote:
each modifier inventing its own rules can't be a good idea.
Why?
The helo + nohelo example: A policy can set one of these flags,
and redirect to another policy without the mutually exclusive
flag. If that other policy later adds the mutually exclusive
flag the effect is unclear. Implementations not supporting one
or both of these options won't (necessarily) note the problem.
An implementation supporting both would report the MUST NOT as
PermError. We're not interested in PermErrors which are hard
to reproduce.
It's a variation of the exp= MUST NOT, a common strategy "all
modifiers including options affect the record where they stand,
they don't cross include: or redirect= boundaries" is clear.
A strategy "each modifier (or option) defines its own rules"
could result in rare and hard to debug errors.
Frank
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