[standards-jig] Pubsub "Real World" Implementation Issue

Bob Wyman bob at wyman.us
Thu Jul 24 18:02:13 UTC 2003


Peter Millard wrote:
> Section  9.5 defines "Meta-Nodes" which are nodes which 
> contain meta data about the system itself, including all 
> "public" nodes, etc.. It's exactly what your describing here.
	Sorry, I missed that when reviewing the latest draft. As you
have it, it looks like it will do the job although it is a bit
disconcerting to see no norms defined for what metadata should be
provided when describing a node. I believe it would be very useful to
define a few fields as being things that are recommended for use. These
would include things like "creator," "description," "creation date",
"publisher", etc.
	Also, there seems to be no defined mechanism for a node creator
to say whether or not the node is "public." In fact, I can't see
anywhere else in JEP-0060 where the concept of Public or Private is even
mentioned... It would seem that more specification is needed here.

	The text says: "enables subscribers to be informed when new
nodes are created." How about the case of an existing node being
modified? For instance, if node configuration is used? I think I should
be able to get a message published to me when such a thing happens.
Please consider changing the text to: "enables subscribers to be
informed when new nodes are created or modified."

	A problem that may be discovered on some systems that host many
nodes is that there could be a large number of nodes being created and
or modified given any period of time. In many cases, any particular
client will only be interested in a small subset of the total number of
node creation events. For this reason, I think it would make sense to
have folk consider supporting some form of filtering for subscriptions
to the meta-node. Given the example you present of a node having a
"creator" field, I should be able to limit my subscription to the
meta-node so that I only see nodes that are created with a "creator" of
"creator at jabber.org." Similarly, in Stephen Pendleton's example of a
PubSub service that shows people's location, there might be an
"application" field in the form with value "locator" and clients might
just want to subscribe to meta-node messages that concerned nodes that
had the application="locator" value.

		bob wyman




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