I'm currently scoping out the following projects for 0.7:
A) Background synchronization (let the user continue to use Chandler while syncing)
B) User Notification framework (provide the user some way to see that shared items have been changed)
C) Conflict resolution (let the user manually reconcile conflicting changes that have been synced)
Below is a brief description of each, including areas in which I would need help from other groups (Andi with some repository work, and the Apps team for some CPIA work). Comments are welcome.
(A) Background (or "asynchronous") syncing involves moving the current sharing operations into their own thread rather than blocking the main UI thread as they do today. The difficulty here will mostly be in the repository view merging code, since using a different thread requires using a different repository view. I expect I will need some amount of Andi's time to work through view merging issues, and we'll need some way in CPIA to indicate (probably via some animated icon) that a collection is currently being synced. Grant has already done an experiment with moving sharing to its own thread, and I will incorporate that work soon. Some details to be worked out here include what happens if the user is in the middle of editing an item that is modified by a background sync.
(B) User Notifications: I'm not sure if I'm talking about what has been referred to as "big-N Notifications", but clearly what is needed for sharing is some way for the user to see a log of changes that happened as a result of syncing. Currently you can see such changes flash by quickly in the Sync dialog, but Mitch proposed the idea of having a sidebar collection which acts much like an RSS feed of changes. We could add a new Kind to the domain model named "UserNotification" (or some name to distinguish it from any internal notifications). Changes made in the background during syncing would get a corresponding UserNotification item added to the Changes collection. The user could then, at their leisure, scan through the changes via the list view of that Changes collection, and either mark each UserNotification as "read" or else delete the UserNotification item. This same mechanism could be used not just for sharing-related changes, but for any kind of thing that needs to be brought to the user's attention in a non-immediate manner. These UserNotifications could be fed into a single collection, or multiple collections, depending on preference. This requires from CPIA: (1) a way to sort the list view, and (2) some sort of 'mark as read' facility.
(C) Conflict Resolution: In 0.6, when two people change the same attribute on the same shared item and synchronize, the first one to sync wins. The second user gets a notification of the conflict in the Sync dialog, but their local change is lost, overwritten by what the first user assigned. There are a few approaches we could take to provide better conflict resolution: (1) Quarantine all background sharing changes until the user is at a point where they are ready to incorporate all of those changes. The user is then presented with each conflict (either one-by-one or altogether) and they choose from either the local change or the remote change. All conflicts would have to be resolved at this point, otherwise the repository could not continue with the repository view "refresh". (2) Pick an automatic conflict resolution policy ('local changes win' versus 'remote changes win') and when a conflict happens follow that policy, but in addition add a special kind of UserNotification ("ConflictNotification"?) item to the Changes/Notification log collection, recording in it which Item/attribute had the conflict, and what the two attribute values were. I prefer (2); this would allow sharing-related changes to appear at any time (since from the repository's standpoint, conflicts are resolved immediately), and allow the user to review/resolve conflicts at their leisure. Ideally reviewing a conflict would mean clicking on a ConflictNotification item in the list view and being presented in the detail view with a side-by-side comparison of an item -- local changes next to remote changes -- and buttons allowing the user to pick between the two. This project would require some CPIA work for presenting a conflict resolution detail view.
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