Axis (NISO JATS table model)
A method of categorizing table cells. The value of this attribute should be one or
more category names. (This attribute is based on and
intended to be converted easily to the XHMTL axis attribute.)
|Text, numbers, or special characters
||Names the conceptual axis or a comma-separated list of axis names.
|Restriction: @axis is an optional attribute; there is no default.