Describe each of the characteristics about the engine:
What data needs to be transmitted between the client and server. Try to keep this as small as possible.
How one would create threads within the Core Engine.
The configuration data used to initialize the Core Engine.
Describe what the server will store and process.
Describe what the client will store and process.
Describe what the interface will look like. Possibly, provide a mock up.
What kind of information are we monitoring. How will we display it to the user.
How will a user manage the modules.
A list of modules to be created with a description on how they work. Each module will need to describe a management side and a client side.
Most of these elements will have their own design documents.