constructor daemon vs. constructor library

At Mon, 15 Jan 2007 12:00:48 -0500,
Jonathan S. Shapiro wrote:
> 
> On Mon, 2007-01-15 at 09:42 +0100, Marcus Brinkmann wrote:
> > At Sun, 14 Jan 2007 07:21:38 -0500,
> > "Jonathan S. Shapiro" <[email protected]> wrote:
> > > Libraries are a tool that you should only reach for when the performance
> > > cost of engineerability becomes prohibitive.
> > 
> > You are conflating separate issues.  If you want address space
> > separation, then there is no reason why the C library can not spawn
> > arbitrary helper processes to execute the algorithms desired by the
> > user.  I leave open the question for now if this makes sense in this
> > case or not.
> 
> Sigh.
> 
> Marcus: when people speak of implementing libraries they generally mean
> that the algorithm runs in the same address space. It is you who are
> conflating issues here.

You need code to call the daemon which presumably is in a library.
Why is that so much simpler than spawning a new process which performs
the same function?