I need to richly tag all posts and very dynamically filter them based on these tags site-wide.
Let's take a car-site as an example. I need to get all posts related to volvo four wheel drive:
I know how to accomplish this for a single site, using something like this: http://wordpress.org/extend/plugins/query-multiple-taxonomies/
How can I query site-wide posts using their taxonomies? Or some other approach?
All input is welcome.