title: iOS app - architecture/sample for synchronizing CoreData against Web-Service
body: <p>I am looking for either a sample app or a more architectural discussion to build an app, which maintains a local persistent store (CoreData) and keeps it sync against a Web-Service like Flickr. In my case it is Salesforce, but the pattern should be similar to many apps for Flickr, Twitter, IMAP and so on.</p>
  
  <p>Sample questions: 
  where are the best points to invoke the syncing?
  what are proven datastructures to maintain local changes
  - maintain a "changed" BOOL in the local store for every unsynched change; I would prefer a field level flag against a record level flag)?</p>
  
  <p>Of course I have to optimize this on my own, knowing the amount of records (100's) and changes (10's per day)  and the probability of conflicts (low in my case on a field level).</p>