System and Session Bus

[Oliver Frommel]

> 
> >In order to have my application communicate with other
> >programs running in my desktop session I would connect to
> >my session bus. In practice that would mean most applications
> >would need to connect to both busses.
> 
> No...
> 
> I don't expect most applications to need to connect to the system bus at 
> all. Why should my text editor need to know my hardware device listing?
>

Not the text editor maybe, but:
- most sound software (USB audio and midi devices)
- software for digital cameras 
- video editing software (IEEE1394)

In these cases I would connect the application to the system bus 
and register them for events of the appropriate devices of the
Hal service. Additionally I would have to connect to the 
session bus to make the applications scriptable or exchange 
data with cooperating applications.

> And if you answer accessibility hooks like text-to-speech or other input 
> devices, I don't expect *applications* do to that by themselves, but for 
> it to be handled by a library or external process.
> 

Well in that case the application (text editor) would 
have to communicate with said library or process. 
Assuming that you want the application to be notified
when the user plugs in e.g. a braille reader it should
be a library/process being capable of async notifications.
I thought this was exactly what DBUS is for.

Thanks for your help
Oliver