Windows 95 and Windows NT make a very open and explicit Printer Provider
interface. In the DOS and Windows worlds, this has been implemented at a
"redirector" - really deep, under the covers, fairly "unknown" to the OS
itself, lives a redictor that traps interrupts and puts itself between the
application and the low level OS port interfaces. If a job comes it it
"steals" the job away from the OS and "redirects" it out to the network. It
can also have configuration information in it os send along (not runtime)
but preconfigured job attributes to cause certain behavior of the back end
job processiong instrcutions. In the Novell world, this was done with the
capture command. When I "captured" the port, jobs would be redirected with
the parameters set a capturing time. There are also similar redirectors in
the OS/2 and OS/2 Warp worlds, but I forget how formal the interfaces are
(that is if it is a more low level "redirector" interface or a higher level
"provider" interface).
Scott