[TUHS] Difference in purpose of /var/spool vs /var/lib

Can anyone enlighten me on the effective difference in the use of /var/spool vs /var/lib? It's my understanding that spools are for files that are in transit. Effectively like packages moving through a shipping depo or people waiting in line. I.e. they come in, they hang around for a while, and then they leave. I'm of the opinion that files in /var/lib should stick around longer and are not nearly as dynamic (if at all, save for code updates). As sure as I type this, I can't think of a reason library files would go under /var vs a different */lib directory. Does it make any difference if the files are actually executed and / or consumed on the system? I don't consider the POP3 / IMAP / NNTP server to be processing files when people access messages / articles (read: files) via the respective protocols. Back story: I'm considering writing something that will download a file every day and process the last day's / week's / month's file(s) to generate output which is itself stored elsewhere. - I feel like these files should live in the /var/spool/<bla> subdirectory. -- Grant. . . . unix || die