* the corresponding action will enable it (at least this is the idea).
* \li Enabled elements which variable's weight is non-zero. They are utilized in some LMM functions.
* \li Active elements which variable's weight is non-zero (i.e. it is enabled) AND its element value is non-zero.
* the corresponding action will enable it (at least this is the idea).
* \li Enabled elements which variable's weight is non-zero. They are utilized in some LMM functions.
* \li Active elements which variable's weight is non-zero (i.e. it is enabled) AND its element value is non-zero.