> A single global, mutable tree of untyped text is a bad persistence model. In a strict sense, almost all software accessing standard hierarchical file systems

> A single global, mutable tree of untyped text is a bad persistence model. In a strict sense, almost all software accessing standard hierarchical file systems is even just broken -- it breaks for certain concurrent operations, and there is no way to forbid them. But still hierarchical filesystems are the best usable-by-default model I know. It's a humane approach from a cognitive standpoint: the real world of "things that exist only once, in one place" is inherently hierarchical. For different needs, it's often easy enough to flatten data a bit and use tools like filename globs or regular expressions, to get a performant, good enough solution that is also maintainable. For very specific needs, you can always use a relational, or whatever, DB.