I'm looking for a set of words that define a logical, hierarchical structure to define a simple 3 level taxonomy, but it needs to comply with the following requirements:

1. The words must be related, like for example category->subcategory or species->subspecies->family are.
2. The words should be very general, so I can apply them to any subject.
3. The hierarchy must be well-defined and acknowledged.

I was thinking about something like theme -> topic -> subject, but one could argue that topic and subject are the same thing. Is there another combination I could use? This comes from someone who does programming for a living, where this kind of things are very usual and easy to achieve.

Thanks.