But we’re not Drupal,
Trust me - I know that.
and we like our visual tree hierarchy.
I like it too, that’s why I learn ModX now ;-) and I didn’t mention Drupal feature to provoke cms vs. cms mud fight.
What I learned about taxo was how end-user (editor of content and users) liked it in Drupal-based site.
So - one can have only one static tree hierarchy represented by parent-child documents. And that concept is clear for everybody.
But when it comes to describing content - scalable tagging structure, independent from content hierarchy is very helpful sometimes.
Eg. if you have asus p4 laptop, 1gb ram and 40gb hd, maybe you want to compare it with other models out there. So you would like not only to follow "static tree" created by editor (other asus stuff from that year), but you would like to enter "processors tree" and find other stuff in p4 branch or jump to another brunch - core duo.
Alternatively - there could be ram memory tree, or HD tree. Or maybe screen resolution. Whatever you want - taxonomy provides alternative ways to navigate, with their own structures, own breadcrumbs etc.
I think this is pretty natural way of dealing with any "content" - and it is quite easy to explain to your client, at least I was lucky with it.
Compared to Drupal, Joomla etc Modx’s document/menu structure is fantastically elegant and simple to use so let’s keep it that way!
Of course. I do not want to say Modx should be designed like this or that. But taxonomy is sth you can find almost eveywhere (eg bothany), only we do not usually know it’s named like that. If two guys - X and Y are hungry and in search for restaurant, X may be looking for specific kind of restaurant (pizza or sushi?) while Y would prefer one located as close possible (Brooklyn or rather Manhattan?) and it has nothing to do with document structure imho. Taxonomy is mere "meta describing of content".
Besides - I’m really impressed with Modx now ;-) although I do not understand it very much.