[ZODB-Dev] RE: changing PersistentMapping to PersistentDict

[Jeremy Hylton]

I made the change from PersistentMapping -> PersistentDict in ZODB4.
The ZODB4 code base will not be compatible with ZODB3 (the current
version).  Instead the goal is to fix problems without concern for
compatibility.  

Like the Zope 3 project, I can imagine that some features of ZODB4
could be backported to ZODB3, or that we could create a compatibility
layer that would mitigate the issues.  In general, though, ZODB4 has
as little concern for backwards compatibility as Zope 3.

Jeremy