Empty cells are cells in a table that do not contain any content, such as text or elements. These cells are often used for layout purposes or to create a specific structure in the table. Empty cells in DITA tables can be handled by using the <entry> element with no content.

Empty cells can be useful for creating layouts or aligning content in tables. For example, they might be used to create spacing between cells, maintain consistent column widths, or structure a table for future content insertion. The empty cells are often styled to have no visible borders or background to ensure they don’t affect the table’s appearance.

Example:

        <table>
          <tgroup cols="2">
            <colspec colname="col1" colwidth="1*"/>
            <colspec colname="col2" colwidth="1*"/>
            <tbody>
              <row>
                <entry>This cell has content</entry>
                <entry class="empty-cell"><!-- This cell is empty --></entry>
              </row>
            </tbody>
          </tgroup>
        </table>
    

In this example, the second <entry> element is an empty cell used for layout or spacing purposes within the table. It maintains the two-column structure of the table, even though it contains no visible content.