Missing markup element: trace of a matrix

Dear Sirs,

   I was reading your specs for MathML, and I noticed that there was no
operator defined for the trace operation on matrices. (The trace of a square
matrix is the sum of the diagonal entries of the matrix.)  While the trace
of a matrix is not used as frequently as the determinant, I think that it is
used often enough that a content markup element be defined for it.  

Thank you,

Joe Gottman