[vos-d] new vos concept: listen conditions

[Peter Amstutz]

On Wed, Jan 31, 2007 at 09:52:11AM +0100, Karsten Otto wrote:
> Funny... always before, VOS basically was a system for object state  
> replication. However, what you describe sounds more like a publish- 
> subscribe system! I wonder whether this paradigm shift is truly  
> intended? Or is the "subscription" just a way of optimizing network  
> traffic?

This isn't so far off as you put it -- the listener system has always 
been closer to publish/subscribe system than a straight replication 
system: it's used to propagate events inside the program as well as over 
the network, and caching the value on the local side is supposed to be 
an optimization, not a mechanism for making a guaranteed full copy.

That said, I want to revisit the issue of replication in the s5 design, 
since we have embedded properties that will allow for the replication 
(and persistance and caching) systems to be smarter about how to handle 
values when they change.  Indeed, the whole design of VOS is predicated 
on the idea that we can maintain fine-grained representation of the 
scene and still be efficient by batching and filtering synchronization 
and updates.

> Also, I don't quite understand the way this is supposed to be  
> implementated. Does every vobject have to understand the subscription  
> language, restricting the updates it generates? Or do they behave as  
> before, but the site filters updates by subscription before sending  
> them over the network?

It would be on the vobject.  When the property changes it would 
determine if it thinks you are interested in the update or not.  The 
subscription language would be optional.

-- 
[   Peter Amstutz  ][ tetron at interreality.org ][ peter.amstutz at gdit.com ]
[Lead Programmer][Interreality Project][Virtual Reality for the Internet]
[ VOS: Next Generation Internet Communication][ http://interreality.org ]
[ http://interreality.org/~tetron ][ pgpkey:  pgpkeys.mit.edu  18C21DF7 ]

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