Really, all software I ever used uses the file path to reference a file. Traktor, Rekordbox, Serato, Ableton, Logic, Photoshop, Aperture, Lightroom, Xcode, should I stop here? If you move the file it is missing by definition for any application that references that file. Rekordbox is the only other competitor that has hardware that uses USB sticks as a database, and copies the files to the USB storage device itself, your USB stick is a completely closed system in Rekordbox. But it still uses it’s own database format on top of a regular FAT filesystem. Engine gives you a bit more freedom, but with freedom comes more possibilities to break things.
You can NOT add random data to a system database like the filesystems TOC. a filesystems TOC has a strict format so it can be read by any operating system supporting that filesystem. Randomly adding fields to the filesystems TOC would break any support by such operating systems, and therefore would be a new database format on it’s own. It would very much likely break the ability to boot from this volume too. Any bug would further risk catastrophic data loss. your FAT/TOC is off limits for user space! A TOC bridges the gap between user space software and kernel space, and there is a good reason there is such separation. If not we would be catapulted back into the MSDOS era of single-user/single-tasking operating systems, were full control over hardware was handed over to the application.
PS, from the other thread:
Thats another thing you have backwards: scanning a filesystem, opening each file, and reading the metadata from it is very CPU intensive. If you want a load time of a few seconds instead of a few minutes up to a few hours (depending on database size) you really need a database centralizing all this info. 1 specialized database file is faster than parsing this info from 10.000 files, containing mostly information irrelevant for browsing purposes (99.9% is audio, 0.1% is ID3 tags). You would have to read a few gigabytes of data instead of a few megabytes… On top of that, tracks and playlists have a many-to-many relationship, while tracks and folders have a one-to-many relationship. Not using a centralized database would mean you have 2 or more hard copies of one file if you want it to appear in more than one playlist, wasting disk space. Smartlists would be impossible.
Really, with all due respect, @DeJulius, if you think that you can just add columns with information to a filesystems TOC then you do have a lot of misconceptions on how computers work…