In the MathML specification it is stated that `The matrixrow elements must always be contained inside of a matrix'. This is not the case in OpenMath where the matrixrow symbol can appear on its own. A matrix row encountered on its own has no MathML equivalent. However, when it is encountered within a matrix object, then translation is possible.
As we mentioned earlier, it is possible to translate a matrix defined with matrixcolumns to MathML. However, if a matrixcolumn is found on its own it does not have a MathML equivalent.