ReadonlycodeReadonlydocumentWhich document kind rejected the input.
ReadonlyfoundThe version value actually present, whatever its type.
ReadonlypathSlash-path to the offending place, rooted at /. / itself means
the whole document.
ReadonlysupportedThe versions this build reads.
The document declares a version this build does not read.
Carries the version found so a host can tell the user which one it has, which is the difference between an actionable message and "unsupported version undefined".