RE: Mutliple event components

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

> The default (main) component is the header. In going to several components we
> are splitting the body into pieces. I've called these pieces clusters. Each
> cluster is a cluster of event components that are stored together. They don't
> have fixed names because they don't have fixed make-up, but they do need to have
> names, assigned when they are created. The name will live in the cluster header
> (which references each of the event components in the cluster and is the OID you
> use in the retrieval of the cluster). We have to put the cluster names into the
> event header too, come to think of it, in order to look up the OIDs.
> 
> The user specifies he wants clusters "A" and "B", the OIDs (or filenames, for
> non-Objy components!) corresponding to these clusters are looked up in the event
> header, and then the OIDs/filenames can be retrieved by GC. Translating from
> cluster name to OID/filename deals with the experiment-specific event
> architecture and should be on the experiment side of the interface, shouldn't
> it?
> 
>   - Torre

Torre,

There are 2 situations for files on tape, corresponding to "clusters": those 
stored into objectivity, and those "non-objectivity" files.

In the first case, each event component in a "cluster" (e.g. tracks) has an OID.  
We are planning to return the OIDs of all event components in the clusters 
requested for the qualifying events in each query.

In the second case, of "non-objectivity" files, is there something that 
distinguishes the event components in a cluster (cluster pieces)?  An offset and 
size in the file would be reasonable.  That would be the equivalent of OIDs for 
non-objectivity files.  If we have this in the index, we can pass this to the EIs, 
thus saving the trouble to read an entire file when only some of the  pieces are 
needed (just as we do with object_id lists).  If so, these need to be generated 
and stored in the tag database (and our indexes) when these non-objectivity files 
are created.

What do you think?

Arie.