Tassilo Horn <tassilo@member.fsf.org> writes:

> Another issue is updating.  There the question is: Can I update package
> A without breaking any other package that needs it?

The package management system in Debian has two things to deal with this

1) Packages can explicitly depend on versions of their
   dependencies. This is mostly used to make libfoo-dev version 1.2.3
   only get installed with libfoo version 1.2.3

2) Sonames. When there is an ABI change in a library, there's supposed
   to be a "soname bump", which in Debian means actually changing the
   name of the package. It seems to me that one could simplify this
   slightly by having a "soname-version" field to perform the same
   function.

One thing to bear in mind is that shared libraries on unix are probably
a simpler problem than emacs libraries: I can install multiple versions
of libfoo and the dynamic linker will select the correct one for an
application. Trying to install multiple versions of an emacs package
would result in a godawful mess, because it's not just a list of
functions that can be called.

I don't know how one could solve that, so I suspect that the only
solution is to only allow one version of a package at once. I notice
that (for debian, at least) transitions between these incompatible
packages are non-trivial to organise at best.

Rupert