Major Description
we had a quick discussion yesterday regarding enforcing uniqueness
of jcr:uuid and how we are want/can assert that.
in contrast to what was said yesterday in the meeting the jcr:uuid cannot
be expected to be always a system generated random uuid. That's only true
for those cases where a referenceable node is created using Node#addNode
or Node#addMixin("mix:referenceable"). However, this is not the case when
content is imported using Session#importXML or Workspace#importXML. in these
situations the generation of the jcr:uuid is not governed by the system.
exporting and re-importing items is very likely to produce uuid-collisions
and we need to make sure we can verify and assert the uniqueness in these
cases.
from the current layout i think that a ValidatorProvider present during
commit validation would be the right place for such an assertion. in order
to verify the feasibility of that i approach i added a UUIDValidator to
the oak/identifier package some days ago (validation not yet implemented).
if we find out that this is not suitable or reliable we probably have to
look for a solution closer to the mk.
in any case (and irrespective of the final solution) we should make sure
we understand the (potential) limitation of the uuid-uniqueness in a
clustered environment, make sure our implementation gracefully deals with
potential violations and have limitations documented.
maybe it was also wise discussion under which circumstances such
inconsistencies could be really harmful and where it might be acceptable.
