RE: Handling ROOT files

[Arie Shoshani <arie@math.lbl.gov>]

Mark, thanks for the quick reply.

> There is no file ID (or system name in objy lingo) for ROOT file in a
> central repository.
> Just the file name, no different than if it was an ascii file.  The list of
> file names could be generated by a listing of files in HPSS directories.
> There is a TChain class that represents a collection of root files which
> will be used for an analysis pass.  It has methods to get the list of files
> in the chain and so on.
> http://root.cern.ch/root/html/TChain.html

I suspected that this is the case.  I think we'll have to generate file IDs 
internal to the Storage Manager, and maintain a map to the real file names.
The CM will then get the names of the files from that map.

> I guess the ROOT Tagdb could have for each entry the filename and event
> number, even though seems a bit wasteful, it might be an easy direct
> approach.  The data is compressed before writing to disk so it will not be
> such a big deal.  Since the Tagdb for the ROOT version has yet to be
> designed it can contain whatever information needed.  One could pass the
> list of filename + event IDs in that file to analysis code.

What we need to know is that we do not have to pass anything but the event
id set for the events that qualified.  So, we rely on any additional info that 
the User Code needs to be in the TagDB.

Arie.