I doubt Ito’s design ideas have anything to do with Kahn’s (let’s not forget that formal essentialism in Japan is exemplified by Arata Isozaki, who influenced Ito’s early buildings – and who has used plenty of rather un-European vaults in his 80′s buildings), Plus to me they look more like stalactites anyway. Ito has extensively used vaults and arches in buildings such as Silver Hut or the Yamashiro Museum so check those out to see where he’s coming from. Oh, and the most important thing – masonry is extremely hard to come by in Japan. Bricks are expensive over there and builders are not familiar with the material. Sejima refers to those white brick flats she did as “experimenting with new materials” so both Kahn-style arcges and Mediterranean-style vaults are out of the question.

What those arches ARE is a clever solution to the contradicting demands of a) a transparent space where different actions, images and information come and go continuously AND b) a complex, maze-like urban space with different intensities of phenomena, so that said phenomena aren’t rendered flat and static (i.e. monumental, permanent, essentialist, Kahn-like as in “teaching is to gather under a tree” or “arches are a shape that resides in bricks”). So hats off to Mr Ito for finding a simple answer to such a complex contradiction.

As for the messy organisation of the shelves, I guess it has to do with his idea of “microchip-like floor plans”, as exemplified in the Sendai Mediatheque.