BeOS did it by writing their own filesystem. The filesystem author wrote a good book about the design and implementation, including overviews of other filesystems (eg NTFS). He has made the book available for free download at http://www.nobius.org/~dbg/practical-file-system-design.pdf
The way it implemented the queries well was because they were integrated into the filesystem. Windows/Mac/Linux do it in userspace. Doing it in the filesystem would be considered a layering violation by most.
Layer violations are fine if they give you value. ZFS is very layer "violating" as well. However, the layers are concepts put in place by humans to help, not God given laws of nature.
Agreed, and if you run on a microkernel, then pretty much everything is in userspace and any boundaries are those of, say, a capability system for security purposes. I still cannot wrap my head around the fact that we're adding ways to avoid the kernel network stack and other exceptions to the rule, while ignoring microkernels as the sorely needed feature for mainstream computing it is.
Ars Technica also has a nice 2010 article: http://arstechnica.com/information-technology/2010/06/the-be...
The way it implemented the queries well was because they were integrated into the filesystem. Windows/Mac/Linux do it in userspace. Doing it in the filesystem would be considered a layering violation by most.