But it has problems. For instance, I like to collect information about robotics and artificial intelligence. In many cases I have papers with titles like "Using Computer Vision to Control a Robot Arm via a CNN". Do I put it under "robotics/sensors/vision" or "ai-ml/anns/cnn" or "robotics/motion-control/platform/arm"...or...? It can technically fit into any and all of those categories!
That's a problem with hierarchical category structures; when something can fit into multiple categories, you can either duplicate the information (not good - unless your system has some way of using pointer refs or such to prevent data duplication - which most file systems don't), cross-link the information (put it in a canonical spot and symlink to it), or just say "f-it" and stick it someplace, and hope you can find it later (which sometimes you can't).
What I wish I had, instead, was a simple means to search my filesystem in a very quick fashion. Ideally, it would be something like the old Google Search Appliance, which could spider and index my filesystem, read each file (and any metadata stored in the file, such as in the case of videos and images) and build up an index that can be quickly and easily searched. It would also keep this index up-to-date as files are added, removed, or changed.
Unfortunately, I've yet to find a low-cost (ideally free) open-source solution to this problem, that was also easy to set up and maintain. I've found more than a few solutions (or partials) which given enough admin and configuration (plus maintenance and/or glue code) could potentially become the system I want, but none of them were "turnkey" - install, simple setup (nothing more complex than a NAS or WiFi Router, for instance), and "let it go". They were all very "enterprise-y" and required more than a bit of effort to install and maintain. It isn't that I couldn't do that, I just don't have the time to dedicate to such a task. But it might be something I just have to bite the bullet for.
Maybe what I need to do is research the latest offering of FreeNAS - maybe they've (since the last time I used it) implemented a decent search engine module (or some third party plugin has been created) to handle this issue?