>'unknown' means that the Printer doesn't know what the value is. However,
>the standard isn't clear how job validation works against a value of
>'unknown' on a Job Creation operation.
I agree. I suggest we clarify this to mean that the Printer doesn't know,
a priori, which values it supports. The client is free to attempt the
operation.
For example, suppose Redirect-Job is implemented as an IPP client built
into the Printer. In general, an IPP client doesn't know, in advance, what
Printer URIs it can submit Jobs to. So the Printer can't provide a list of
"redirection-printers-supported". In this case, it returns
"redirection-printers-supported": 'unknown'. The Printer doesn't know
whether or not it can redirect a job to a particular URI until it tries.
-Carl