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Occasionally connected systems

What about offline clients?

Clients can be made to work offline, allowing you to issue commands locally, which are synchronized with the write side when reconnecting.

A client has a tendency to pull in features of the write side (for doing local validation) and of the read sides (for updaing faster than eventual consistency allows). In some sense, since the client is the user's window to the system, it always has a tendency to grow until it looks like a small copy of the whole system including write side and read sides.

What is command merging?

Sometimes in a highly collaborative domain, commands arrive "too late" and the current state of an aggregate has already changed so that the command does not apply cleanly. Command merging is the act of extracting the underlying intent from the command, and then creating and applying a new command from that intent.

How can command merging be done in practice in an occasionally connected client?

The git merging model seems an appropriate one to steal.

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