> Can you explain what's wrong with the concept of a container format that allows embedding subdocuments of different types?

A system managing opaque streams with handler apps registered via GUIDs is pretty much antithetical to open formats for data exchange.

Are you suggesting that a document format should be a monolithic controlled by one organization and is actually more open than one that allows multiple entities to contribute to an artifact without permission or coordination? You can think that if you want, but you have to actually argue for it, not just assert it, because to me, that's closed, not open.

Or is it that you just really hate UUIDs? Me too, man. Should have gone with reverse DNS. It's a technical and aesthetic quibble though.