doubt in Library delay and slew representation

Hi Friends,
I having a doubt in this library

------------------------------------------------------------------------
lu_table_template(fall_delay_table) {
variable_1 : input_net_transition;
variable_2 : total_output_net_capacitance;
index_1("300, 400, 500, 600") ;
index_2("0.003, 0.004, 0.005, 0.006") ;
}

lu_table_template(rise_delay_table) {
variable_1 : input_net_transition;
variable_2 : total_output_net_capacitance;
index_1("300, 400, 500, 600") ;
index_2("0.003, 0.004, 0.005, 0.006") ;

}
---------------------------------------------------------------------
related_pin : "a" ;
cell_fall(rise_delay_table) {
values(

) ;
}
cell_rise(fall_delay_table) {
values (

) ;
}
fall_transition(rise_delay_table) {
values (

) ;
}
rise_transition(fall_delay_table) {
values (

) ;
}
----------------------------------------------------------------

what does these represents.....

cell_fall(rise_delay_table)
cell_rise(fall_delay_table)
fall_transition(rise_delay_table)
rise_transition(fall_delay_table)

what does cell_fall(rise_delay_table), that is the cell_fall represents the output (or) input and wt about rise_delay_table.

in the same way fall_transition(rise_delay_table)....

pls clear my doubt ...

thanks & regards
Venkat