thead — A table header consisting of one or more rows.
thead (db.cals.thead) ::=
Header rows are always rendered at the beginning of the table.
This element is expected to obey the semantics of the CALS Table Model Document Type Definition [calsdtd]. Header rows are often presented in an alternate typographic style, such as boldface.
In paged media, if a table spans across multiple pages, header rows are printed at the top of each new page.