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From Andreas.Schlos...@sybase.com
Subject Re: Less restrictive conflict resolution for fragment imports
Date Wed, 16 Dec 2009 16:48:25 GMT
Richard,

this could also work, but will add more complexity to it. You may run into 
situations were you need to randomly abandon one fragment:

Host imports version [1.0.0,2.0.0), fragment 1 imports [1.0.0,1.5.0), 
fragment 2 imports [1.5.0,2.0.0)

In my approach, both fragments would be exluded, in your approach you have 
to find a tie breaker to decide on which fragment to include.

With my approach, statically determining the valid version range by 
looking at the host bundle, you'd keep the control over valid versions 
with the host bundle and everybody using it can be sure that the host and 
all possibly existing fragments will run when obeying the host version 
range (so, when using a consistent set of bundles you can be sure that you 
can add any fragment you want without updating other bundles). When 
dynamically determining the version range by looking at fragments as well, 
you'd take away this guarantee. It may happen that a consistent set of 
bundles gets inconsistent out of a sudden because of a fragment with too 
restrictive import versions (meaning the fragment does not work).

The dynamic approach obviously has the advantage to be more flexible, but 
I think it should rather be the responsibility of a fragment developer to 
adhere to the version ranges of the host bundle than the responsibility of 
the user of a host bundle to comply to (more restrictive) version ranges 
in fragments he'd like to use.

Maybe it would be interesting to look into how Equinox is doing it, 
unfortunately I don't know. Can anybody help?

Thanks
Andreas


"Richard S. Hall" <heavy@ungoverned.org> wrote on 12/16/2009 08:30:10 AM:

> What I was planning on doing is taking the intersection, which would be 
> the highest floor and the lowest ceiling of each overlapping version 
> range...and of course, if there is no intersection, then they are in 
> conflict and the fragment would be thrown out.
> 
> -> richard
> 
> On 12/16/09 11:13, Andreas.Schlosser@sybase.com wrote:
> > Guo,
> >
> > I think your algorithm is not 100% correct. The host version 
boundaries
> > must lie within the fragment version boundaries. So, looking at your
> > example:
> >
> > 
> >> Host version [2.0.0,3.0.0)
> >> 
> > 
> >> Fail fragment versions [1.0.0], [1.0.0,2.0.0), [3.0.0]
> >> 
> > Fails, since version lies completely outside host version boundaries
> >
> > 
> >> Pass fragment versions
> >> [1.0.0,5.0.0),
> >> 
> > Passes, since host version lies within these boundaries
> >
> > 
> >> [2.5.0,2.9.0)
> >> 
> > Fails, since host version lies outside boundaries. E.g., when host is
> > importing 2.1.0 this would cause fragment to fail.
> >
> > Thanks,
> > Andreas
> >
> >
> > Guo Du<mrduguo@gmail.com>  wrote on 12/16/2009 02:25:50 AM:
> >
> > 
> >> On Wed, Dec 16, 2009 at 12:54 AM,<Andreas.Schlosser@sybase.com> 
wrote:
> >> 
> >>> Hi,
> >>>
> >>> I found that Felix is validating the compatibility of host vs.
> >>> 
> > fragment
> > 
> >>> imports by ensuring that in case host and fragment are importing the
> >>> 
> > same
> > 
> >>> package, they should use the exactly same version (range). I believe
> >>> 
> > that
> > 
> >>> this is a little too restrictive and Felix should also allow the 
host
> >>> bundle to be more restrictive on the version range than the 
fragment.
> >>> 
> > This
> > 
> >>> way, it is still guaranteed that the fragment will run with using 
the
> >>> version range from the host bundle (which is a subset of the 
fragment
> >>> version range in this case).
> >>>
> >>> I just ran into this problem when trying to use the Hibernate +
> >>> Annotations bundles packaged by SpringSource. Hibernate Annotations 
is
> >>> 
> > a
> > 
> >>> fragment bundle, hosted by the Hibernate bundle. Hibernate imports
> >>> org.dom4j;version="[1.6.1, 1.7.0)" whereas the fragment imports
> >>> org.dom4j;version="[1.6.1, 2.0.0)" and the current implementation 
does
> >>> 
> > not
> > 
> >>> allow this fragment to be linked to its host.
> >>>
> >>> What do you think?
> >>> 
> >> +1
> >>
> >> I have this problem with spring-osgi-extender as well. For fragment,
> >> we may enable the fragment when there are common set between host
> >> version and fragment version.
> >>
> >> Host version [2.0.0,3.0.0)
> >> Fail fragment versions [1.0.0], [1.0.0,2.0.0), [3.0.0]
> >> Pass fragment versions [1.0.0,5.0.0), [2.5.0,2.9.0)
> >>
> >> Any drawback to this approach?
> >>
> >> -Guo
> >>
> >> 
> > 
> 

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