# Re: recap: MathML2 2nd WD (long)


Andreas,

I'll just answer the easier questions, I am sure one of my colleagues
will step in later for the harder ones:-)

> -- 4.4.2.7     Shouldn't we have the basic sets in MathML (N,Z,Q,R,C)???
> As it stands, the default rendering for examples as given in the
> recommendation is incorrect since nothing allows the renderer to infer
> that R stands for the reals.
>

They are added this time, in  4.4.12

http://www.w3.org/TR/2000/WD-MathML2-20000328/chapter4.html#contm:reals

but the example in 4.4.2.7 does need updating ti use <reals/> it is
true, thanks.

> -- 4.4.6.1  It's useful to mix condition elements and arguments in sets,
> as in {x\in N | x < 5}  where x\in N is best seen as a <condition> and
> x<5 best seen as an <apply> argument.   (The same is true for lists, 4.4.6.2.)
>

actually it's useful to _force_ that your variable ranges over an
existing set (N here) as that way you avoid Russell's Paradox, but
MathML doesn't force this (in general it doesn't prevent the
construction of meaningless or false expressions)
so in MML it does appear that one would write this as
{x |x\in N and x < 5}
which probably isn't to bad, as syntaxes go.
(There was an extension/change to the set syntax discussed earlier on
this list to allow things like  {x^2 |x\in N and x < 5}
that change didn't get described this draft but (I think) there was