Re: OO problem: Performing actions on messages (very long, sorry)

["per" <commander@death-star.com>]

>But scheduling items are instances not types.

Yes. They are called Actions.

>Instances are unknown.

*Message* instances are unknown when the scheduling takes place.

>OK, why that bunch of actions cannot be just a piece of code in a
task?

The user is not supposed to code, build and load the entire system for
every test. He/she shall schedule actions appropriate to the current
test and run it the system, reschedule for another test and run it etc.
(Scripting in non-realtime is BTW done with Tcl/Tk & Tash.)

>Are you writing an interpreter?

Well, thinking about it - yes, I suppose.

>Shouldn't messages be formed rather in terms of device semantics? And
why
>should they exist before being sent to the devices? Is it a kind of
>premature memory optimization?

1. Device 1 delivers data into the system (which also can be looked
upon as a kind of router not caring too much of message contents)

2. The system intercepts the data (a Message) letting the user
manipulate, display, record etc the data according to a preprogrammed
schedule (created by the user, in form of a list of different Actions,
not hardcoded in Ada etc etc). In this sense the system must "know of"
the message contents.

3. The system delivers the data (Message) to Device 2.

Gentlemen, my problems are solved thanks to a hint in one of Dmitry's
earlier  examples. I'll now settle with that.
I thank you all for your efforts.