<dd>The "attributes-charset" and "attributes-natural-language" attributes as described in section 3.1.4.1 of the IPP Model and Semantics document.
- <dt>"device-class" (type1 keyword):
-
- <dd>The client OPTIONALLY supplies a device class keyword to select which devices are returned.
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<dt>"exclude-schemes" (1setOf name): <span class='info'>CUPS 1.4/macOS 10.6</span>
<dd>The client OPTIONALLY supplies a set of scheme names that the requestor does not want to discover. If the client omits this attribute, the server responds with devices of all schemes specified by the "include-schemes" attribute.