models.dat file wasn't installed

I installed hplip on vector linux 5.9 (a slackware deriviative). I could never get scanimage -L to find my USB connected OfficeJet 6500, although sane-find-scanner always found it. hpaio was present and loaded (I used the SANE_DEBUG_DLL setting specified on the troubleshooting page to determine this). hp_check -r gave a positive result (it complained about missing python qt4 support, but I didn't need it). I finally determined (again following your excellent troubleshooting by tail -f /var/log/syslog while invoking scanimage -L) that the models.dat file wasn't being found.

Turned out that only the images and localization dirs were under /usr/share/hplip/data-- once I copied the rest over, scanimage -L, and, finally, xsane, found the scanner and worked.

I wish I could tell you the exact ./configure settings (for hplip) which got me that far, but I went through so many iterations of configuring, making, and installing that I couldn't tell you much except that
1) I always disabled qt4 and fax support
2) At the end I was disabling hpijs support, because I finally realized that they were no longer necessary
3) I always enabled scan and cups (but not necessarily newcups, wasn't sure what that was) support

Maybe the best thing to do would be to emphasize (on troubleshooting scanning problems, http://hplipopensource.com/node/333) looking at syslog while running scanimage -L EVEN IF it doesn't find your scanner. That's what clued me into the uninstalled models.dat file.

Thank you so much for your excellent product and hard work!