My files are a mess, I try to structure them into folders with names that describe what they are in a recursive class break-down sense but later on I have trouble finding the file again when I go looking for it (the one file can possibly exist in many folders).
What file system will allow me to find my files by a combination of tags instead of using folders?
If there was such a file system, I’m not sure how OSes would cope, being so deeply dependent on the folder system. I came across tag2find, which isn’t too bad; it solves my problem with finding stuff for now but it is an application, not a file system.
What you are asking for is a Database File System. I know of one experimental implementation for Linux called DBFS. Microsoft started developing Windows Future Storage (WinFS) – it was planned to ship with Vista but due to technical problems the project was delayed and as far as I know finally canceled. NTFS is also capable of storing metadata for files but not to an extend of a full featured database file system.
The integration of such a file system into an operating system should not be that complicated for the core of the operating system – it can simply stick with the hierarchical model. The complex part is the (graphical) shell that must expose the structure and capabilities of the file system to the user.