Each entry for a media feature defined in the Media Queries spec has a field titled "Applies to" that specifies which media types or "media groups" the media feature applies to. The datatype library should do checking for instances of media features used with media types they do not apply to. It's not clear from the spec whether such instances are conformance errors, so it may be that we will need to just report them as warnings.

For example, "print and (scan: progressive)" should be reported as "The 'scan' media feature does not apply to the 'print' media type."