<http://schema.org/keywords>
"staircase, stairway, step, ladder, Treppen, Treppe, Stufen, Leiter, escalier, \u00E9tape, \u00E9chelle, escada, degrau"^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.bibliocad.com/library/extern-stair--semi-circular--shelf_12438>