[OSM-talk] License plan

[MP]

>> - if you decide to delete contributions and those contributions are
>> only part of the history of objects, do you rollback  to a previous
>> version of these objects ?
>
> Rollback to the last version before any changes incompatible with the
> new licence are made.

This could be perhaps "optimized": if user A creates some
highway=road, user B changes it to residential and user C changes it
to secondary. A and C agrees to new license, B won't.
But contribution of B was completely removed by C's edit, so it won't
be necessary to revert to highway=road in this case. Basically, if the
edits of "incompatible users" got later reverted or altered so their
contribution is not there anymore, there is no need to rollback, just
delete their revision from history.

This could help in cases where user B just make lot of mistakes that
got later reverted/corrected.

Technically, for ways we would have problems with restoring old
revision, since the nodes referenced by the old revision could have
been moved/deleted in the meantime, so that would possibly create some
invalid data.

> There is the idea floating around that modifications to existing data
> are insubstantial, and successive contributions could potentially be
> kept without issue, but I think it is safest to remove them.

Perhaps for really minor changes, like alterations to created_by or
conversion from "true" to "yes" or alike we could make an exception.
Or in cases where the object was "completely modified" from the last
"license-incompatible" version.

> In the interests of keeping it clean, any reverts made due to
> incompatible changes would not be kept in the history.

Would there be at least some information like "this object was
reverted because of new license" (which would signal that the object
perhaps need to be re-improved somehow) and for deleted objects
information that "something was deleted from here"?

> A backup can be kept of the old database of CC-by-sa compatible data.
> It might come in handy if some non‐responders pipe up and say “yes”, or
> the “no” voters change their minds.

Won't be of much use after longer time, since the missing data are
probably first to get readded and merging contribution of people who
changed their mind with the parts that was restored by remapping the
affected area in meantime would be difficult and won't be posible to
automate.

Also, what if someone who disagrees to new license deletes some data
(either because that data is wrong or is replaced by something else
that he draws). Will the deleted data get restored?

Martin