When we turn on workflow reduction, we tell pegasus that we already have a file, say foo.txt, by adding an entry for foo.txt to our RC. When pegasus plans the workflow, it stages in the foo.txt we already have so that other jobs can run, but it also stages it out again, which makes little sense. I think pegasus should assume that, if we already have an RC entry for a file, then we do not need that file to be staged out to the output site.