At this point I understand the comparison to a relational database, but I don't understand what that buys you -- why would you want a three column table for this relation? I imagine you'll explain this more later, but breaking the second sentence into its own paragraph and adding a short example motivating the three-column relation (like, "this way we can do resources.r.server to get all the servers that host a particular resource, regardless of the path", or something) would be helpful for me.