Re: [tycho-dev] [discuss] tycho repository layout and metadata format

["Sievers, Jan" <jan.sievers@xxxxxxx>]

>Not sure I understand. Does this "bill of materials" list all target
>platform IUs or does it provide additional constraints to help the
>resolver choose among multiple versions?

yes, the idea was to have a locked-down list of IUs, each IU has a fixed version (perfect version match).
If it's not in the list, it won't be resolved.
Together with artifact immutability this guarantees build reproducibility if we build against one "global" repo that keeps aggregating new versions. 

>One of aspects of build reproducibility is ability to make small changes
>to the project, to produce a bugfix for an old release for example. This
>implies ability to make small changes to target platform definition and
>expect corresponding small changes to resolved target platform. I don't
>think resolved target platform "snapshot" provides this property.

Actually we value strict build reproducibility over ease of use 
for doing patch releases. E.g. if I want to do a patch release of my product and in this patch release I need to consume
a newer version of a 3rd party library (and possibly its transitive dependencies), I have to go and change this list of IUs.
IMHO it's OK if this is not cheap as long as reproducibility is guaranteed.

Regards,
Jan