This function is introduced solely for the purposes of translating it via SKSI into the SQL function 'X' which is defined in the the Open GIS Simple Features Specification for SQL. (OGCX Coordinate Fn POINT) returns the value of the first coordinate of POINT, where the order of the coordinates is determined by the data structure representing POINT in the underlying database. See also the corresponding CSQL function, CSQLX Coordinate Fn