The finer grouping layer beneath this atlas's eight driver type categories, minted across building, style, architect, architectural-material, organization, milestone, concept and element so each can be browsed as a set of human sized groups rather than one long flat list. Building and style entities group by function or period, architect entities share style's eight period-based bands, architectural-material and element carry their own dedicated material and structural-vocabulary bands, and each subcategory carries its own prose explaining what belongs in it and what does not.