At the December IPP WG meeting, we agreed that an "xxx-supported" attribute
that has only one value SHOULD be a READ-ONLY attribute. However, I think
we meant if the implementation *as reflected in the factory settings* has
only one value. Therefore, the following statement that was added to the
Set spec needs clarification:
For a Printer attribute that is normally settable, if a Printer object only
supports a single fixed value for that attribute, it SHOULD NOT include that
attribute's keyword name in this attribute's value. For example, if a
Printer only supports "sides" with a 'one-sided' value, then the
"sides-supported" keyword SHOULD NOT be one of the values of its
"printer-settable-attributes" attribute.
I suggest the following update to the "printer-settable-attributes"
attribute:
For a Printer attribute that is normally settable, if a Printer
implementation only supports a single fixed value for that attribute, it
SHOULD NOT include that attribute's keyword name in this attribute's value.
For example, if a simplex output device only supports "sides" with a
'one-sided' value, then the "sides-supported" keyword SHOULD NOT be one of
the values of the IPP Printer's "printer-settable-attributes" attribute.
However, if an administrator changes an "xxx-supported" attribute to a
single value, that attribute SHOULD NOT become READ-ONLY and that
attribute's keyword name SHOULD NOT be removed from the
"printer-settable-attributes" attribute.