Comment # 3 on bug 969961 from Michael Andres

(In reply to Luiz Angelo Daros de Luca from comment #2)
> I though that prereq was currently the same as require for RPM:
> 
> https://www.redhat.com/archives/rpm-list/2003-June/msg00173.html
> 
> So, this does not apply for zypp?

I had to lookup the code in libsolv to describe the exact behavior. AFAIK the
resolver tries harder to keep pre-requirements when breaking up cyclic
dependencies. Without cycles the result should be the same.

> 32-bit equivalent (at least, pam-config doesn't). However, AFAIK, there is
> no way to specify a hard-conditional dependency, only the soft-one using
> supplement+packageand.

right

> Wouldn't it be interesting to *try* to install all supplement of a package
> just after it was installed and before any other package that requires it?
> Specially for pam modules, nothing requires its 32-bit variation and it is
> ready to be installed just after the 64-bit was installed. Who is
> responsible to define the installation order? libzypp? libsolv?

That's done in libsolv. You could open an issue at
https://github.com/openSUSE/libsolv to discuss this.