[IPP] Use of unknown and no-value attribute value tags

[IPP] Use of unknown and no-value attribute value tags

Ira McDonald blueroofmusic at gmail.com
Thu Sep 15 22:05:00 UTC 2011


Hi Mike,

I like all of it, except that in printer-geo-location we should
get rid of that MIB-centric "unknown" and instead use the
semantically equivalent "no-value".

Cheers,
- Ira

Ira McDonald (Musician / Software Architect)
Chair - Linux Foundation Open Printing WG
Co-Chair - IEEE-ISTO PWG IPP WG
Chair - TCG Embedded Systems Hardcopy SWG
IETF Designated Expert - IPP & Printer MIB
Blue Roof Music/High North Inc
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On Thu, Sep 15, 2011 at 5:56 PM, Michael Sweet <msweet at apple.com> wrote:

> All,
>
> I've received a few queries about how the "unknown" and "no-value"
> attribute value tags are used in IPP recently.  What I've been telling
> people is basically the following, but I'd like to document this somewhere,
> perhaps as an errata for one of the IPP RFCs (probably RFC 2911 and 3380)
> along with some updates to the IPP registry for the affected attributes.
>
> Comments?
>
>
> The "no-value" Attribute Value Tag
>
> This value may be set or returned for any settable Job, Subscription, or
> Printer attribute. The typical usage is to specify an xxx-default Job
> Template attribute that has no default value, such as
> "orientation-requested-default" - in that case the Printer may apply a
> default based on the document such as automatically applying
> "orientation-requested" with a value of 4 (landscape) for a landscape
> document.
>
> The "no-value" value may also be returned for read-only description
> attributes that are a mandatory part of an object.  For example, the Job
> object's "time-at-completion" attribute can be returned as "no-value" when
> the Job has not yet entered a terminating state.
>
>
> The "unknown" Attribute Value Tag
>
> This value may only be set or returned for specific Printer attributes.
> Currently only the proposed "printer-geo-location" attribute has been
> defined to potentially have an "unknown" value.
>
>
> __________________________________________________
> Michael Sweet, Senior Printing System Engineer, PWG Chair
>
>
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