[panic]

Yeah, this "two-layer storage paradigm" is exactly what I'm getting at. There are a lot of other ways you could slice it, though. System services want simple APIs with high performance -- they'd prefer not to pay the cost of the higher-level user document representation.

Personally, I think user documents shouldn't be a kernel concept -- it should be a protocol implemented by user-space system services. This would let any app expose its storage as "documents" without having to change its internal representation.

[snuxoll]

The concept is nice, but every time somebody has tried to implement it there has been some miserable failure either from a business or technical sense. See the Be File System for the former, and WinFS for the latter.

In fact, the only successful implementation of the concept (even if only partially) I've seen is the object-oriented storage on IBM i (formerly i5/OS and OS/400).