Store each workflow run trace in it's own directory
The ppod-gui module includes enhancements to the Kepler GUI for browsing and viewing the traces of previously run workflows. Each trace is a single, XML-formatted file, and the traces are organized in folders named according to the workflows run. These folders corresponding to actual directories on the user's machine. Double-clicking on a trace opens it in the provenance browser.
I suggest that instead of putting all the traces of runs of a particular workflow in the same directory, we create a new directory for each run (in the directory named for the workflow) and place the trace there. This would support: (a) including multiple traces output from a single run (possible with COMAD); (b) storing a copy of the workflow in the run directory so that the specification of the executed workflow is not lost; (c) using this directory as the default location for other files produced during the run (and possibly temporary directories holding intermediate files useful for resuming an aborted run, say); (d) summary reports generated for the run; (e) copies of input data; etc.
Adding another level of directories would add to the work of navigating to the latest trace, but this would not be a problem if we automatically opened the trace using the provenance browser at the end of each run (as suggested in Bug 3546), and if we provided an additional view of recent traces that hid this extra nesting.