A table contains all of the control variables and also a set of
                            table specific variables. These table specific variables can be
                            queried but not dynamically changed. In order to change these values
                            in a table, actions are provided: gra.table.resize,
                            gra.table.scroll.  The variables are as
                            follows.
| grd_rows | 4s1 | The number of rows in the table | 
| grd_cols | 4s1 | The number of columns in the table | 
| grd_visible_rows | 4s1 | The number of visible rows in the table | 
| grd_visible_cols | 4s1 | The number of visible columns in the table | 
| grd_active_row | 4s1 | The row index of the currently active cell | 
| grd_active_col | 4s1 | The column index of the currently active cell | 
| grd_row | 4s1 | The table’s current top left row | 
| grd_col | 4s1 | The table’s current top left column | 
| grd_xoffset | 4s1 | The x pixel offset that will be used to determine the origin of the 1,1 table cell | 
| grd_yoffset | 4s1 | The y pixel offset that will be used to determine the origin of the 1,1 table cell |