I identify the hierarchy as the source of my problems. I don't need hierarchy, and when I use it, it's because that's the one tool I have. There's no hierarchy between time and place, and I shouldn't be forced to establish it.

There might be some hierarchy between tags: PhD/laser experiment, PhD/dissertation, but there's rarely a need for it to be more than 1-2 levels deep, so I prefer to suffer the pains of inadequate hierarchy rather than inadequate queries. Or at least I would if I could try it out.