Isn't "transitive" the wrong word?

[Janice Caron]

On 04/04/2008, Manfred Nowak <svv1999 at hotmail.com> wrote:
> Janice Caron wrote:
>
>  > So the relation is
>  [...]
>
>  y is reachable from x (through a series of pointers for example)
>
>
>  Reachable is transitive:
>
>   if z is reachable from y
>  and y is reachable from x
>
>  then
>
>     z is reachable from x
>
>
>  In D the transitivity of reachability carries over to const:
>
>   if x is const
>  and z is reachable from x
>
>  then
>
>     z is const

My apologies for being thick, but I still don't get it. What /exactly/
is the binary relation R, such that:

(1) (a R b) and (b R c) implies (a R c), is true in D
(2) (a R b) and (b R c) implies (a R c), is false in C++

I still can't figure that out. Am I just missing something obvious?

And even assuming there is such an R, wouldn't it make more sense to
say "R is transitive", rather than "const is transtive"?

Help me - I'm confused.