Row headers in tables can be defined using the rowsep and rowsepentry elements. These elements define row headers in a DITA table. Row headers typically label the columns of the table, providing information about the data in each column. Their key attribute is rowsepname, which assigns a name to the row header.

• rowsep: The rowsep element is used to define a header row in a DITA table. It serves as a container for row header information. The rowsep element must include one or more rowsepentry elements.
• rowsepentry: The rowsepentry elements are used within the rowsep element to define the individual header cells. Each rowsepentry element corresponds to a specific column in the table and provides the header text for that column. The rowsepentry elements may contain the name of the column or other relevant header information.

        <table>
          <title>Product Comparison</title>
          <tgroup cols="3">
            <colspec colname="col1" colnum="1" colwidth="20%"/>
            <colspec colname="col2" colnum="2" colwidth="30%"/>
            <colspec colname="col3" colnum="3" colwidth="50%"/>
            <thead>
              <row>
                <entry colname="col1">Product</entry>
                <entry colname="col2">Features</entry>
                <entry colname="col3">Price</entry>
              </row>
              <rowsep>
                <rowsepentry>Specifications</rowsepentry>
                <rowsepentry>Product Highlights</rowsepentry>
                <rowsepentry>Pricing</rowsepentry>
              </rowsep>
            </thead>
            <tbody>
              <row>
                <entry>Product A</entry>
                <entry>Feature set A</entry>
                <entry>$100</entry>
              </row>
              <row>
                <entry>Product B</entry>
                <entry>Feature set B</entry>
                <entry>$120</entry>
              </row>
            </tbody>
          </tgroup>
        </table>
    

In this example:

• The thead section contains a header row with regular entry elements to label the columns.
• Below the header row, the rowsep element defines a second row with rowsepentry elements that serve as row headers. Each rowsepentry element corresponds to a specific column, providing header information.
• The rowsepname attribute, which can be used in each rowsepentry element, assigns a name to the row header, such as “Specifications,” “Product Highlights,” and “Pricing.”