On Oct 24, 2005, at 8:03 AM, vlado wrote:

Many of us in Amsterdam discussed nested sets as a promising solution to our
widespread neet for hierarchy. I encourage Konstantin and others to pursue
this solution. Book.module is also excellent test case IMO.

I think Aliie, has a prototype of a hirarchy module in her sandbox as
well

Thanks for noticing!

I've been trying to explain what Moshe and Konstantin describe succinctly - that relating items (not just nodes) is a universal problem that deserves a more comprehensive solution than what can be handled by an adjacency model. I've seen the adjacency model in a heavily-related system, and it wasn't good.

The other concept in hier is that it's not all about nodes. I'm proposing a system that includes users, nodes, terms, even the website itself. And I'm proposing that we investigate permissions handling there too.

I hope to be part of this conversation as it progresses, and I would love to spend more time on the hier module. As is often the case, I seem find myself with time OR resources, but never both.

I'm compiling a writeup on a variation on the nested set algorithm,
which should help with frequently changed nested sets - to avoid
frequent re-indexing.

I agree that thrashing on a heavy-update system would be the biggest problem with a nested set algorithm. My first modification was to introduce a depth field to be able to move about the tree more easily.

More important are the inserts and deletes. There are proposals out there which "leave room", so the tree is only re-hashed every n modifications, which I hope will be useful.

I think it would merit thinking through an approach, where we use
"specialised" indexes for different ordering types like linear, tree,
graph, etc...

I hope we can try a few of these out and benchmark them against realistic data. Unless there are clear delineations for what works when, I'd lean to a "one size fits all" approach. Of course, I'm saying this without the benefit of context.

I was really, really, REALLY bummed about not being able to make Amsterdam. Hopefully, financial constraints won't stand in my way next time there's a DrupalCON. I hope you all had a great time!