Randy,
On 2012-11-01, at 8:28 AM, Randy Turner <rturner at amalfisystems.com> wrote:
>> Should we include (enumerate) some examples of how to accomplish advertised functionality WITHOUT device-local caching?
I think it is important to address the stream vs. spool use cases, but I *don't* think we need to enumerate the implementation options for each type of printer. As Pete pointed out, IPP already handles such things as copies and duplex where at least some content needs to either be cached by the printer or the job has to be aborted so that the client can resubmit when an exception occurs. I don't see fax retransmission as any different, aside from some new job-state-reasons values to tell the client what happened.
> This would correct any false assumptions about job caching being required to accomplish certain advertised functionality.
>> print(fax out) by reference is a good example whereby my device can support complete job retries without local caching (as you say below)
That isn't really true in the general case, since the printer needs to cache at least some of the remote content in order to render/print/fax it and not all remote stores allow random access to the data making retries potentially resource intensive.
I often see "print by reference" being heralded as the fix for all of our woes, but in reality little has changed since we introduced it some 15 years ago - it works for certain specific use cases but is no substitute for the client supplying the print data because a URI generally does not contain all of the information needed to reproduce what the client would supply to the printer (beyond credentials/cookies/etc., the software used to generate the printable content and any client-side processing intent). Having the client be the server for the reference solves some of those issues but places an undue burden on the client implementations and introduces a lot of issues on mobile devices (fax, then walk away and the printer cannot access the document to be faxed) - better to just make sure direct, streamed printing/fax can be supported by both sides and let print/fax-by-reference be a bonus/optimization option that is available.
Also, for fax-out we can't assume that the printer can produce a cover sheet or that the client would want it to. More than likely the client will want to supply the cover sheet for the fax, which means direct printing or print-by-reference with the client as the server.
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Michael Sweet, Senior Printing System Engineer, PWG Chair
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