Special form of synchronize where delete is prevented on one side of the sync

[drkast]

I need to accomplish the following:

We are synchronizing part of the network drives onto dropbox (for business) by using FFC to sync files and folders from the network onto a large HDD on a specific computer, from which we use Dropbox software to sync everything onto the Dropbox cloud. Great for accessing office data on an iPad etc.

In order to prevent users from deleting folders from their Dropbox accounts, we want to synchronize in the following way:

Network >>>>> CREATE >>>>> Dropbox
Network >>>>> MOVE >>>>> Dropbox
Network >>>>> UPDATE >>>>> Dropbox
Network >>>>> DELETE >>>>> Dropbox
DROPBOX >>>>> CREATE >>>>> Network
DROPBOX >>>>> MOVE >>>>> Network
DROPBOX >>>>> UPDATE >>>>> Network

but not
DROPBOX >>>>> DELETE >>>>> Network

So whatever is DELETED in the Dropbox folder, will not be deleted on the network folder.
In fact, any deletion done on a DROPBOX folder is to be disregarded first.
Then at the next sync (after 15 min), FFC notices that there is something on the Network and nothing in the Dropbox, and ADDs it back to Dropbox.

However, when a user creates new documents in the Dropbox, while traveling or using his iPad, this file needs to be successfully synchronized onto the network.

The reasoning is: when users work on their computers at work, they deliberately delete a folder that is no longer needed. But when a user connects his Dropbox account to his computer which then runs full of data, and then starts to delete files and folders, we want to prevent that from deleting whole folders on the network.

I created a user that has NO DELETE rights on the Network, and disabled the lock files as described here:
viewtopic.php?t=1338
with the following change in the GlobalSettings.XML:
<LockDirectoriesDuringSync Enabled="true"/>

However, now it doesn't delete any files.
Even when I delete files on the network, they are sync'ed back to the network from the dropbox folder, whereas deletions on the Network folders should result in deletions on the Dropbox folder.

Any suggestion appreciated.
Happy Easter!

[Zenju]

I guess the simplest and most straightforward solution is to not deny any deletions on the network drive: from a higher-level perspective deletion is just one type of modification, which can be create, update or delete. Whether deletion is dangerous OTOH is a low-level decision depending on the specific application to which the files belong and cannot be answered in general. Deletion can be data loss, but so can overwriting a file with invalid data.
In order to protect from accidental data loss due to deletion and overwriting, the versioning feature could be used, if Dropbox doesn't offer such a function already.