[danseagrave]

Talk of tag/DB based file systems always reminds me of WinFS[1]. Microsoft were trying to build a tag (well relational database) backed file system since 1990... eventually abandoned - presumably due to back-compat issues.

1. https://en.wikipedia.org/wiki/WinFS

[jpfed]

Lots of reading material about the conception and death of WinFS: http://www.metafilter.com/134799/WinFS-what-it-could-have-be...