Remarks

From the Elsevier DTD, used mostly within mathematics, when ordinary MathML underline and overline functions are inadequate. The Overline Start and Overline End elements act as milestone tags marking the start and end of overlining that may extend across element boundaries.

The Overline Start and Overline End elements enable creation of overlining in content, most commonly in mathematical content, where a normal Overline tag (<overline>) would break the XML rule of being well-formed that no two elements may overlap. The overline created using these two elements can have arbitrary start and end points because the start and end elements are paired through the use of the unique identifiers (IDs), not as the start and end of a single element. For example, in the text “ABCD”, if the text “ABC” is to be overlined and the text “CD” is to be underlined, ordinary overlining with <overline> would create invalid tag overlap. The text could be correctly tagged, using the Overline Start and Overline End elements as:

 <overline-start id="overline"/>AB
 <underline-start id="ul1"/>C
 <overline-end rid="ov1"/>D
 <underline-end rid="ul1"/>