My thought was the same as Kosta... that we would delete and replace any updated file.
FYI, here's what I'm planning on doing in the UI (which is in charge of monitoring the file updates):
1. When first opening a solution it sends all files to the indexer. The indexer should determine whether each file needs to be indexed or not according to the file's timestamp.
2. When a solution is open and a file is saved the UI sends this file to the indexer to be indexed.
Given this approach of the UI should we store timestamp with each element so that the indexer will know when to update a given element or ignore it? We may be able to just store <timestame, filename> outside of the index and then ignore updates
to files that haven't been changed since they've been updated.