Re: DBus IDL (Was Re: GLib plans for the next cycle)

[Rob Taylor <rob taylor codethink co uk>]

Brian J. Tarricone wrote:
> Mark Doffman wrote:
> 
>> I understand that there is no difference on-the-wire between a
>> function-call and message passing. The difference is in peoples
>> perceptions and expectations.
>>
>> When I read CORBA IDL and see:
>>
>> int AFunction (int, int);
>>
>> Because of the connotations provided to me by years of procedural
>> languages I expect this function call to be synchronous. I hope to break
>> these perceptions by providing a message-based IDL.
> 
> I don't have this perception; I think you're mistaking your own
> perceptions for the majority's.
> 
> One of the huge benefits of this entire exercise is to "hide" dbus calls
> and make them look like methods on an object.  If you're going to avoid
> calling dbus methods "methods," then I fail to see the point.


I think you're confusing describing the wire format of a message bus
protocol with language bindings. Personally I would like to avoid that
confusion which caused a good few problems in the CORBA days.

> Whether or not the object is local (in-process) or not is irrelevant.
> Whether or not the method call is sync or async is also irrelevant. It's
> a method call, pure and simple.  DBus itself even calls them method
> calls.  All you're doing by avoiding that in the IDL is making us learn
> and remember yet another confusing and incompatible syntax.

Wow. No.

That was the main insanity of CORBA. Hiding that something is IPC
results in you thinking things are working one way when in fact they're
working completely differently and subject to a load of unexpected
failure modes.

Other things to consider here is that hiding IPC can also result in
hugely inefficient IPC because you end up designing a pretty API rather
than efficient IPC.

I could rant at length here about the various benefits of CORBA vs
message bus. But suffice to say hiding that there's a message bus means
you end up with CORBA again and all the attendant problems.

> I ask you to *please* reconsider not using some normal method-call
> syntax for the IDL.  There's really no reason to do otherwise.  If there
> really is a perception problem, people need to fix that on their own.

Thanks,
Rob

>     -brian
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-- 
Rob Taylor, Codethink Ltd. - http://codethink.co.uk