I have a couple of questions on ROOT data storage mechanism, which could be
interesting for many people especially from large collaborations.
- is it possible to read an event written by somebody else in the collaboration
back without knowing *everything* about the event format?
In "ZEBRA world" if I have an event (a set of ZEBRA banks) written out,
I can always read it back as a set of ZEBRA banks, and then use only those
banks I need, without knowing the exact format of the rest banks.
- I heard that people have encountered certain difficulties with using
versioning mechanism provided by Objectivity. So let me ask (I apologize
for not trying this feature in advance) how the versioning mechanism
works in ROOT? Suppose I've written several data files out using
ClassDef(MyClass,1)
for MyClass. Then I changed the definition of the class (say, added one
more data member to it) and now am using
ClassDef(MyClass,2)
and trying to read the data written in "old" format back. How does ROOT
know about the differences between version 1 and version 2 of MyClass?
Thanks a lot, Pasha.