Defines the @valign attribute, its values, and default for use in attribute lists in NISO JATS table model (based on and designed to be converted
easily to the XHTML 1.1 table model).
The NISO JATS table model parameter entity is used in the same way as the equivalent
parameter entity in the XHTML 1.1 table model. Since this parameter entity was named in the same
way as the XHTML 1.1 Tag Set equivalent, it does not follow
the naming conventions for this Tag Set: it is in mixed not lower case, and the separator character is a period, not a hyphen.