I have had some internal discussions around an issue I would like to resolve
across the IPP WG.
ISSUE: An IPP Client sends a print request with the
"ipp-attribute-fidelity" attribute containing a value of 'true'. The client
also supplies the job template attribute "sides" with a value of
'two-sided-long-edge'. The IPP Printer does not support two sided printing.
The IPP Client software generates the request but put the
"ipp-attribute-fidelity" in the job attributes group instead of the
operational attributes group. What should the Printer do?
A) Reject the request with 'client-error-bad-request' since
"ipp-attribute-fidelity" is in the wrong group.
B) Reject the job because the printer does not support two sided
printing. The IPP Printer would accept "ipp-attribute-fidelity" even though
it is in the wrong group. The printer would return a
"client-error-attributes-or-values-not-supported' error and return the
"side" attribute and value in the unsupported attribute group.
C) Accept the job and print it substituting 'one-sided'. The IPP Printer
uses the defaulted value (i.e. 'false' ) for "ipp-attribute-fidelity" since
it was not an operational attribute. The return code would be
'successful-ok-ignored-or-substituted-attributes' and the "sides" and
"ipp-attribute-fidelity" would be returned as unsupported attributes. (i.e.
"ipp-attribute-fidelity" is not a supported job template attribute)
As an IPP Printer implementer I would chose C. The response informs the
client that it is in error. The Printer is forgiving and the job is
printed. The extensibility of IPP is maintained.
The Implementer's guide with need to be updated to provide a recommendation
on how to handle "misplaced" attributes. There is currently a clause that
lumps "misplaced" attributes with missing or duplicate attributes. (section
Xerox Architecture Center
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