Re: Motion 26: NO
On Thu, July 28, 2011 17:34, Nate Hayes wrote:
>
> -- Not giving any specification for how intersection and union handle
> decorations means users will invent their own (probably wrong) rules,
> i.e.,
> what is the standard? Examples were given that show how incorrect handling
> of decorations with intersection or union can lead to catastrophic
> failures,
> so this is not something that should be left up to users.
I had given an example where Motion 27 gives erroneous results for
decorated intersections:
The expression f(x)= x/((x+1) intersect x^2) is undefined for any x in
[1,3], but Definition 7 claims a safe answer for f([1,3]).
It is far better to have no decorations at all for union and intersection
than to have decorations based on a logically faulty basis.
According to Motion 26 (which explicitly forbids mixed bare/decorated
interval operations), such users will get an error when trying to
propagate intersections with decorations. Thus they'll not use it. If they
work around these errors by decorating things by hand, it is at their own
risk, as in any programming language.
The inexperienced user will probably use union and intersection only for
handling domains (where no decorations are required), not for handling
ranges. The latter requires expertise no matter how the decoration
scheme is devised.
Arnold Neumaier