Glen,
There is an explanation in the introduction - I'm happy to expand on this or highlight it differently if you have suggestions...
On Nov 1, 2011, at 3:50 PM, Petrie, Glen wrote:
> Thanks for explanation, it helps. Unless, I missed it, there should a similar explanation in the specification; so that people writing clients will understand the rational when using the preferred capability.
>>> In your first statement, you state that the “printer could” versus the “printer will”; therefore, I assume the “”use”” of “preferred” is optional and that the client could return an invalid job for your example. So, is the User in control of whether they want a printer to use “preferred” value. I assume the Print Client could respond to difference in the sent and returned job ticket in various ways (and mostly likely should). Can the Print Client tell the printer not to use preferred values even if the printer supports preferred values?
>> Glen
>>> From: Michael Sweet [mailto:msweet at apple.com]
> Sent: Tuesday, November 01, 2011 2:38 PM
> To: Petrie, Glen
> Cc: ipp at pwg.org> Subject: Re: [IPP] Please explain the use of "preferred" attributes
>> Glen,
>> The semantic definition is that the Printer may return substituted values for unsupported attributes in a Create-Job, Print-Job, Print-URI, or Validate-Job response. That is, if you specify duplex printing on transparency media, the printer could return sides-preferred with "one-sided" or media-col-preferred with a media-type other than transparency to tell the client that it will print the job differently than requested.
>> In the case of attributes like "copies", a printer may normally support up to (for example) 999 copies for uncollated output, but may only support 99 copies for collated output. Or the printer may not be able to support copies for a given document or document format.
>> In short, previously all the client has known is that particular attributes or values were not supported (or conflicted), but not what attributes would be used by the printer instead (typically the default values).
>>> On Nov 1, 2011, at 12:37 PM, Petrie, Glen wrote:
>>> Discussion on wd-ippjobprinterext3v10-20111013
>> In Section 6.4 I don’t understand the idea of “… the Printer would prefer to use”. Does this the Printer will override Job Ticket values? While, the printer has limitation or constraints which are reported in the capability information; what does it mean when the printer has “copies-preferred” (section 5.3.2) – does this mean the User wants 3 copies but the Printer prefers to only print 2 !!! Very Strange. There could be a concept of “recommended” attributes that would apply to a very small set of attributes (copies is not one of them) and would be presented to the User in such a way as to identify it as “recommended”.
> n The same comment applies to almost all the other “preferred” attributes.
>> Glen
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