Subject: Re: SDP "category" or "thread" field

From: Mark Handley <[email-masked]>
Date: Wed, 03 May 95 15:01:46 +0100

>First, I'd avoid specifying in detail how an application might display 
>sessions (or not). As was said before, this is a protocol, not an 
>application. (Which doesn't mean that we shouldn't be thinking about 
>how things might get implemented, naturally.) Applications may decide 
>that wildcard filtering (*.beatles), implicit hierarchical filtering 
>(comp.protocols matches any comp.protocols.*), etc. are the right thing.

I agree we shouldn't be specifying any algorithm - I was just trying
to indicate how it might be used, and therefore how it might not work
as well as I first thought.

>There's actually a strong disincentive to creating random categories if 
>you want widespread distribution/visibility, as receivers will likely 
>have to know about your category to have your announcement show up. On 
>the other hand, I'd expect 'affinity groups' to create the equivalent 
>of local hierarchies. e.g., gmd.radio within GMD.

Again, this is a UI issue, but I would normally expect that the
default might be to display the top level category if it's unknown.
If the default is not to display then discovering new conferences may
get tricky.  Thus there might actually be incentive to create a new
category to get your announcement seen.

I 'spose we could have a "category announcement protocol", and only
allow categories being announced by a category server to be used to
create new sessions :-) 

>The algorithm is simple: whichever newsgroup you post announcements to, 
>you use in your SDP field :-) It seems to me that the existing Usenet 
>hierarchy could serve reasonably well; people also tend to have a good 
>idea as to what's generally appropriate for the existing groups 
>(spammers etc. excluded), avoiding having to come up with new group 
>descriptions.

Actually I don't think this is a good idea.  Maybe when the number of
mbone users is similar to the number of usenet posters then it might
be OK, but for now I think we want far fewer categories and should not
encourage new cataegories until it's strictly necessary or finding our
existing conferences could be a problem!  It's the managing of the
transition from now to then that concerns me.

>I assume you were also thinking about 'cross-posting'? (Once you allow 
>multiple groups for the same announcement, keywords become a kind of 
>degenerate hierarchy).

You could presumably add multiple "category" fields - the equivalent of
cross-posting.  

I'm not sure "category" is the right word for this.  Jon came up with
"threadlet" :-)  

Mark