My example is of doing "self-discovery" to see if all needful database components seem to be properly installed.
E.g. - the app needs pgcrypto, intarray, and a custom data type. The install script can consequently inform the production folk either "looks good", or, alternately, "seems problematic!" Actually, I haven't coded a sample of the "look for custom SPI & types" part, but it's a natural extension of what I have. Of course, it only provides a legitimate test when run on the database server, which isn't always how production folk want to do it, but that's part of a different argument...
