Classifying pages requires slotting them into a global structure; either hierarchical, or faceted and multi-dimensional.
But there are problems with such classification schemes. You have to understand the whole in order to slot things into place.
If you don't understand the whole, it's hard to get it right.
Typing of links is an alternative to classifying documents. Instead of saying "this page is about this topic", you just say, "that page has an X relation to this one." That allows you to use only local knowledge of the two pages when making the link.