Messaging Middleware Vs RPC and Distributed Databases

I would like to know your opinions o开发者_高级运维n advantages and disadvantages of using Messaging Middleware vs. RPC and Distributed Databases in a distributed application?

These three are completely different things:

• Message Oriented Middleware (MOM): A subsystem providing (arbitrary) message delivery services between interested systems. Usually providing the ability to change messages' content, route them, log them, guarantee the delivery, etc.
• Remote Procedure Call (RPC): A rather generic term denoting a method of invoking a procedure / method / service residing in a remote process.
• Distributed database: seems quite self-explanatory to me, refer to wikipedia.

Hence it's hard to tell specific (dis)advantages not knowing the actual distributed application better. You could be comparing RPC and MOM. In that case MOM usually is a complete message delivery solution, while RPC is just a technical mean of inter-process communication.