Before diving headfirst into a tree-based ontology, please (re)read this essay by Clay Shirky: Ontology is overrated, in which he makes the case that ontological classificationis is a bad strategy when your domain has a:

and your participants are:

In such cases a del.icio.us-like tagging system would make more sense, he argues.

In reply to Re^2: Anyone doing anything about questions/answers at PM? by BioGeek
in thread Anyone doing anything about questions/answers at PM? by johnnywang

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