I've been on an experimental journey for the last few days to figure out if we can use rules to format outlines, and I think the answer is yes. I have a new version of worldOutlineSuite.viewOutline that works with rules, and now I can do very MORE-like formatting with outlines. I think this is going to give the worldoutline a bunch of new applications. But it pays to go slowly here, and do it right.
On 2/1 I made a list of types that are outlines, and those that are not. As a result of this work, two types that were considered outlines are now not -- directory and html. There's nothing that rules can do for them at this time. Here's why.
directory -- A directory of course is displaying an outline. But it's different from the others is a very basic way. They only represent a one-level slice of an outline. This is the web-way to navigate large structures with includes and different document types. At this time we don't have a way to do either in the outline. And because HTML is not as flexible as QuickDraw was (or at least my understanding of how it works is not as complete) it's not likely that we'll be able to use outlines as indices of other document types. So outlines and directories have different strengths.
html -- There's no real point in flowing html types through rules, and the current implementation is so efficient, and rules are pretty slow, relatively speaking. html nodetypes are great for their simplicity and staying out of your way. Outlines on the other hand are in your face, but for a good cause. :-)
BTW, not sure about thumblist. Will probably leave it out for the time-being.
So the types we're going to suck into outlines are: blogpost, howto, code, tabs. The types may remain in the user interface, and in the OPML, but the implementations will all flow through the rules engine, and you will be able to use rules in writing any of these, to over-ride the built-in style choices, and to design your own.
Somhow rules connect up with macros and the glossary, though I haven't thought much about it yet.
BTW, rules are not new. They appeared in MORE in 198x and in Pike in 2000. This implementation is not as powerful as the one in MORE, it had a better user interface, and had more control over the appearance on the page. On the other hand, the web didn't exist then, so it had no ability to network. Pike was a pretty quick project, but good code. In fact, I took the code from Pike and dropped it into my 2012 code. There was one decision I didn't agree with so I changed it. But the rules engine is actually very sophisticated, and it was nice to not have to re-invent it! :-)