Alex Fink wrote:
> Anyway, there are no uncontroversial examples of natlangs
> with the ior vs. xor distinction.  Latin _aut_ vs. _vel_
> is often cited: _aut_ is supposed to be exclusive, _vel_
> inclusive; but I think better the story that goes _A aut 
> B_ means "A or B, it matters which", and _A vel B_ means
> "A or B, it doesn't matter which", where the "or" in the
> glosses doesn't care about clusivity.

That's about it, I think - at least as regards the general 

Under _aut_, the Lewis & Short dictionary says:
"In general it puts in the place of a previous assertion 
another, objectively and absolutely antithetical to it, 
while _vel_ indicates that the contrast rests upon 
subjective opinion or choice, i.e. _aut_ is objective, _vel_ 
subjective, or _aut_ excludes one term, _vel_ makes the two 

OK - _aut_ excludes one term, but then so, normally, does 
_vel_; but in the case of _vel_ I'm indifferent as to the 
choice.  If I'm going to buy a burger or a hot dog for 
myself and friend and there's plenty each available (and I 
ask him in Latin!0, I'd probably use _vel_. But if the only 
two remaining items were one burger and one hot dog, where 
in English I'd say "Do you want the burger or the hot dog?" 
then the choice has obvious implications for me as well and 
I'd use _aut_.

Under _vel_, Lewis and Short say:
".. disjunctive conjunction to introduce an alternative or 
preference, or as not affecting the principal assertion."

_vel_ is indeed derived from the root vel- ~ vol- that we 
find in the verb _volo, velle, volui_ "to wish, want". i.e. 
_vel_ had the idea "what you will".

BUT - things are never that simple in a natlang   ;)

In treating the various different uses of _vel_, Lewis and 
Short give examples where _vel_ is used with the *same use* 
as _aut_ above; they also give examples where the 
disjunctive meaning is very weak and the conjunction 
practically means "and". Maybe that's the source of the 
assertion that _vel_ = IOR.  It doesn't.  It covers a range 
of meanings, mainly XOR, in fact, where the choice is not so 
important (but sometimes it is) to just plain AND.

Lewis and Short give examples where _either....or_ is 
expressed by _aut....vel_ and others where it is _vel .... 
aut_      :)

"Ein Kopf, der auf seine eigene Kosten denkt,
wird immer Eingriffe in die Sprache thun."
[J.G. Hamann, 1760]
"A mind that thinks at its own expense
will always interfere with language".