[SyncEvolution] Getting the concepts clear (Was: Configuring a target)

Part of the confusion may be understanding the need for two sides to the sync. Here is my best go at explaining what is going on. Firstly, forget about the actual task we are trying to do: think about a traditional sync done by SyncEvolution. In that case, SyncEvolution is syncing a local database (files, Evolution, KDE, whatever) with some remote device (mobile phone, etc). In that case, you set up two, related pieces of information: a "source config" (for example @Local), which defines the local database you are trying to sync (and what folders it contains -- known as sources), and a "sync config" (for example MyPhone@Local) which defines how SyncEvolution communicates with the peer, which actual folders should be synced to this particular peer, what sorts of syncs should be done, etc. If you have multiple phones, you might set up multiple sync configs for the same source config -- each one tells SynceEvolution how to handle syncing with that particular device peer (for example, you might sync different source folders with different devices). This works fine if the remote device is a SyncML device, such as a phone. But it also works if the remote device is another instance of SyncEvolution running on a different host. In this case, you would set up another similar configuration on the other host (maybe you would create a source config on that other host called @OtherHostFiles, and a sync config on that other host called FirstHost@OtherHostFiles). Of course, you would set up the sync configs involved (one on the first host, the other on the other host) so that they would talk to each other (one would make the connection, the other would receive it).

The confusion comes when both sides actually run on the same host, in the same SyncEvolution instance. That is what we are doing in your Exchange<->Local sync example. In this case, SyncEvolution optimizes away some of the actual connection details but it doesn't optimize away any of the source or sync configs. That is why you end up having to create a source config for the local files (@Local) and a sync config to tell it what to sync with (Exchange@Local) and also a source config for the Exchange server (@Exchange) and a sync config to tell it what to sync with (target-config@Exchange). The reason the latter has to be called "target-config" is to do with the optimisations SyncEvolution is doing to avoid having an actual SyncML TCP connection between the two sides. It is for the same reason that in Exchange@Local you have to setup a URL as the form local://.