Chris,
> On Aug 6, 2020, at 8:12 PM, Rizzo, Christopher via ipp <ipp at pwg.org> wrote:
>> Trying to find in what IPP spec a requested-attributes value of 'none' is documented.
Sadly, it is not explicitly documented.
However, as it is not one of the registered group names, 'none' literally represents an attribute named 'none', since it is quite likely that nobody will have implemented an attribute named 'none'. :)
> Also wondering what is the purpose of a Get-Printer-Attributes request whose requested-attributes value = 'none'?
The point is more to ensure that an implementation actually supports attribute filtering using the "requested-attributes" operation attribute. Too many printers incorrectly support it, particularly in respect to the registered attribute group names, and this has caused years of interoperability issues as CUPS and other clients have tried to implement driverless printing.
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Michael Sweet