[Standards-JIG] PubSub Whiteboard

Fletcher, Boyd C. J9C534 Boyd.Fletcher at je.jfcom.mil
Thu Jul 1 02:29:16 UTC 2004

We are working on a spec for Scalable Vector Graphics based whiteboarding over Jabber. We are using PubSub for our token passing and as a store for whiteboards. the problem with using MUC is there is no reliable way to get the current status of the whiteboard (wb). Originally we had thought about sending all the wb commands over a separate chat room. When a user enters the conference, they would get a dump of all the wb commands. the problem with this approach is (1) the server must maintain the entire history of the whiteboard and (2) the user must download the entire history of the whiteboard. An alternative would be for a user to ask another user the current wb status and have it sent to them, this is not a very reliable approach. What we decided to do is send all adds/deletes/updates to the whiteboard's pubsub service, so when a user enters a chat room, his client pulls the configuration for the MUC to see if it supports multimedia (note this is a slight change to the MUC config) and if it does what is the JID of the root pubsub node for the room. The room's pubsub node contains the current multimedia capabilites for the room including audio support, application casting support, video, whiteboards, presentations, etc... In the case of whiteboarding, the wb sub-node, contains who currently has the token (allowed to draw), the list of all the whiteboard elements by page number (lines, circles, images as IBB, text, etc...), wb size, current page, number of pages, etc...

This explains why we are having problems with the PubSub spec:

1) we need to have a known consistent way of handling updates to nodes and items in a persistent 
PubSub tree (i.e. the whole 11.3 section discussion over the last couple of weeks). 
2) we need a clear way of handling notification of changes to sub-nodes and items. I think collections will solve this.
3) a change to a publisher's rights to allow any publisher the ability to delete another publishers nodes/items.


> -----Original Message-----
> From: standards-jig-bounces at jabber.org 
> [mailto:standards-jig-bounces at jabber.org] On Behalf Of Nolan Eakins
> Sent: Tuesday, June 29, 2004 9:29 PM
> To: standards-jig at jabber.org
> Subject: [Standards-JIG] PubSub Whiteboard
> Hash: SHA1
> I was reading through the PubSub discussion, and saw the 
> topic of whiteboarding mentioned. I'm not entirely sure as to 
> why you would want to run a whiteboard over PubSub. If you're 
> wanting to whiteboard with a group of people, MUC should do 
> just fine. I was playing with Coccinella one night, and 
> managed to get into jdev with it--no thanks to Coccinella's 
> gui. I opened up my xml console in psi so I could see if 
> Coccinella sent whiteboarding data to everyone else in the 
> room, and it did. Since it made use of <x/> stanzas it didn't 
> show up in regular groupchat clients. They still received the 
> data, but happilly ignored it.
> Basically I see no need for whiteboarding over PubSub. Unless 
> of course MUC is going to be changed so it runs on top of 
> PubSub, but I see no need for that either even though MUC is 
> an extremely basic publish-subscribe service.
> Regards,
> Nolan Eakins
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