While these sixteen top-level categories have remained intact, the ontology of second- and lower-level categories has undergone a gradual evolution; significant changes are initiated by discussion among editors and then implemented when consensus has been reached.
Meskipun tingkat atas lima belas kategori tersebut tetap utuh, namun ontologi kedua dan kategori tingkat rendah telah mengalami evolusi bertahap perubahan signifikan yang dimulai dengan diskusi antara editor, dan kemudian diterapkan ketika konsensus telah tercapai.