[wpkg-users] [Bug 111] Reverse dependencies aka chained installation

[bugzilla-daemon at bugzilla.wpkg.org]

http://bugzilla.wpkg.org/show_bug.cgi?id=111





--- Comment #3 from Rainer Meier <r.meier at wpkg.org>  2008-04-29 14:41:41 ---
I again had a look at this report and it really looks to me as this change is
not required at all. In addition I see quite high risk of problems and
increased complexity here.

Let me explain why I think it is not needed.

You write...
> The installation instructions say "3. Install Notebook software 10." and "4.
> Install Notebook software 10 drivers."

So if this would be a "hard ordering requirement" then point 4 simply _depends_
on point 3. Where WPKG would make sure the software is installed before the
drivers are applied.

However you claim that the drivers could be installed independently as well -
that's why you don't want to set a dependency so you could install the drivers
without the Notebook software 10.
This is most probably true as drivers usually work without additional software
(which sometimes just provide an additional user interface).

So I would rather assume that the the software depends on the drivers even if
the install notes state to install the software before.

If you insist on no dependency between the packages then also the install order
should not make any difference. If it does indeed than setting package
priorities might be absolutely sufficient:
- notebook software 10: priority n+1
- notebook software 10 drivers: priority n

This would make sure that if both packages are added to a profile, then always
the Notebook software 10 package is applied first.
You might think that this coupling is too lose and still allows somebody to
install the drivers first (by just adding the drivers to the profile,
synchronize, then add the software and synchronize again). This is true but it
also applies for "reverse dependencies".
In case notebook software 10 would have the drivers "chained" then nobody would
prevent you to apply the drivers only to the system and adding the software
later on - when the drivers are already there.


> I'm not sure if the "Notebook software 10" will refuse to work if "Notebook
> software 10 drivers" arent installed and I cannot really test this at the
> moment either since I dont have the needed hardware at hand.

Probably you should really test it. To me it looks more like the install
instructions were just numbered while it should be an unordered list (just
install everything listed) or the numbers 3 and 4 could be exchanged.

In general I would say that most likely the software is depending on the
drivers (and not the other way around).


The only difference to what is implemented in WPKG I can see is that your
request specifies somehow "optional" dependencies. Which means to me that a
package is depending on another one if that one applies to the current profile.
If it is not specified in the profile, then also the dependency is not applied.

For example for your software (strictly looking at the most probably invalid
release notes) this would mean that in case a profile specifies "notebook
software 10" and "notebook software 10 drivers" then the drivers seem to depend
on the software and therefore the software should be installed before. In case
only the drivers are applied to the system then the dependency is ignored.


> Another situation where a chained installation would be handy are extension
> for Firefox, updates for Microsoft Office, etc etc ...

No, this I see clearly as a (hard) dependency. Neither extensions nor Updates
_can_ be installed when the application itself is not there. So such an
extension or update clearly depends hardly on the software they apply to.


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