[Zope3-dev] discussion about ObjectHub, EventService etc. (was event-meta.zcml...)

[Gary Poster]

Steve Alexander wrote:
>> are there any security related reasons, why an objecthub should not
>> be referenced directly ? .. no security-related information is stored
>> in it.
> 
> Object hubs and the Event Service are event channels. There may also be 
> other event channels to filter events and batch-up events.
> 
> Whan an event channel notifies a subscriber, that subscriber may do 
> things in response to the event. We need to notify the subscriber in the 
> subscriber's context so that we can get the appropriate security grants 
> for that context. The security grants will influence whether or not the 
> subscriber is allowed to do things in response to the event.
> 
> So, an ObjectHub should not be referenced directly. It needs to have a 
> context so that it can notify its subscribers in context.
> 
> The only things that can subscribe by reference are "leaf" subscribers 
> that don't themselves have further subscribers, and event channels where 
> all of the subscribers to that event channel subscribe by reference

Shouldn't the current "subscribe/globalSubscribe" discussion also 
influence the local event channel subscription pattern in general?  That 
would mean subscribe for all local event channels would be influenced as 
well.

Also: you described at one point the behavior for passing a wrapped 
subscriber into the event service as meaning that the absoulte path is 
obtained and used for subscription, I believe.  Would you buy that you 
first try for a hubid, and failing that, get the path?

Also: use case for a local "directSubscribe" is that the local 
event-channel-like services subscribe directly because these are things 
that are system components and so can have direct (hard reference) 
connections as clients, rather than indirect path subscriptions.  This 
works because of the whole ISubscriptionAware stuff.  ...Do you buy it?

I'd like to try and get the event stuff settled asap because I think I 
can work on it today. :-)

Gary