Dave, my standard caveat when putting words in others' mouths: I think this is what you mean but I'm probably wrong and am eager for correction.

First, I think you're assuming that each multiauthor category is on one topic; no sub-categories within a synthetic feed. Correct? So you could create a Books channel from dozens of categories. But if you want to go further, say categorize into Tech, Fiction, and Non-Fiction Books, we will not break this down further for either the authors or the channel editor; entire new categories will need to be created.

A few riffs on the idea.

Inputs.

The default synthetic channel could be automatic; sources just flow through to html and rss. Or...

Some channels require review/approval by the editor before posting, reflecting trust/confidence and signal/noise of each channel. Suggesting the editor needs a place to

• review/approve individual posts,
• manage channels belonging to a composite feed.

Author points

From an author's view, does a push component make sense? (Send this message about this particular book to that Booklist feed, but not all books I post about.)

A 'join' component? Submit an rss feed to an editor who accepts/declines to add it to one or more synthetic feeds? Request to be removed?

Automatic Acknowledgement: Your rss feed has been added to this composite feed and can be seen here and syndicated there.

Outputs.

Embed sources in the descriptions.

New theme types?

Will the composite have its own rss feed out? If so, can these become recursive? If so, can we have some measure of duplicate-post detection?

OPML file describing the elements of the synthetic channel, so it can be passed around like our orange rss files?

Can I choose to have the synth channel active but not to render? This way I can use the collection of sources to group my News Aggregator feeds by topic without rendering them all to rss or html.