Re: Package priorities and dependencies.
On Mon, 16 Jun 1997, Dale Scheetz wrote:
> On Mon, 16 Jun 1997, Santiago Vila Doncel wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > On Sun, 15 Jun 1997, Dale Scheetz wrote:
> > > Two packages in the list of "important" refused to install because they
> > > declared (correctly) their dependence upon packages of lower priority.
> > >
> > > at depends on libelf0 priority: optional
> > > groff depends on libg++27 priority: standard
> > >
> > > It seems to me that packages of any priority level should not be dependent
> > > upon packages of lower priority.
> > I think this reasoning is wrong: We don't want to install libelf0 and
> > libg++27 because they are "important", we want to install them to satisfy
> > dependencies! The library itself is useless if no program uses it.
> > So IMHO you should have added to your initial list of packages the ones on
> > which they depend, until all dependencies are satisfied. dselect does this
> > automatically. If you don't like it, it is supposed to be done by hand.
> If this is true then there is no purpose served by priorities and they
> should be abandoned. THIS IS NOT THE CASE.
> As I understand it the priority scheme was designed to give a "horizontal"
> installation method. It was intended to provide another selection method
> for performing installation based on a "usefulness" criterion.
> I still argue that for this to continue to be useful it must continue to
> be modular in its design or it looses its usefulness.
> I firmly believe that dependencies should be provided within the same
> priority level or this organizational structure will fail to live up to
> the expectations for it.
I think that the word "priorites" is not that good. We currently use the
"priority" values to define several "subsystems" (cf. policy manual). For
example, the minimal system includes all packages from
"required+important". A medium sized system would contain "standard"
packages. A large system would also have the "optional" packages
installed. (Of course, the user can override these "default selections".)
So, if you enter dselect the first time, it will automatically tag all
packages with priority "important" as "to-be-installed". If you leave the
selection screen, dselect would probably bring you into the "dependency
resolution" screen and would tell you, that you will need a few shared
I think the "sub-systems" defined by the priority levels should be
consistent and thus, a package should not depend on a package with lower
priority level, or the priority level of the latter has to be increased.
-- Christian Schwarz
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