draft-ietf-ipp-implementers-guide-01 says:
> 2.2.1.2 Validate operation identifier
> The Printer object checks to see if the "operation-id" attribute supplied
> by the client is supported as indicated in the Printer object's
> "printer-operations-supported" attribute.
However, draft-ietf-ipp-model-11 does not define any attribute named
"printer-operations-supported".