Use W3C documentation for the XHTML1.1 table model. (http://www.w3.org/TR/xhtml-modularization/abstract_modules.html#s_tablemodule)
This parameter entity holds the INCLUDE or IGNORE keyword to control a conditional marked section, that determines whether the <thead> element is defined.
<!ENTITY % thead.element "INCLUDE" >
JATS-xhtml-table-1.mod