static factory...

[mop65715]

3. A change is an event. Acting upon the 'latest message' is an event. Sockets and dispatch pattern feed upon this type of events. If you still think event handler doesn't go well with your current design, then who is responsible triggering a 'change'? the user?

Again - from my perspective a Dn handler does not need a notification when a Pn message is updated by a Pn handler. A Dn handler's process method is invoked after 'Reads' of Aircraft (A/C) data. Only then will a Dn handler (for those interested in Pn messages) examine a Pn message - which should be the latest message. Pn messages are transmitted (Write) to the A/C.

Again the Pn message could be updated by a Pn handler a 1000 times and written to the A/C before a call to a Dn handler process methods. Until the Dn process method is called the Dn handler is simply not interested in Pn handler notifications of Pn messages.

I guarantee that whoever uses your code must be a contributor to your design. A normal user like me would not dare to use it. In other words, design from the interface point of view, not the implementation.

IMHO, I'll make the same argument about your source. Source snipped..