warnings with sdf annotation

i have used following comand with modelsim simulator

vsim -multisource_delay max -sdfmax
/tb_top/dut_top=/home/projects/user/top_cmax_wc.usdfs.sdf -sdfnoerror
work.tb_top

i am getting following errors
# ** Warning: (vsim-SDF-3262) sdfmax /tb_top/dut_top(90022): Failed to
find matching specify timing constraint.
# ** Warning: (vsim-SDF-3924) sdfmax /tb_top/dut_top: Out of 41689 SDF
statements, 41689 had null values.
# ** Note: (vsim-3587) SDF Backannotation Successfully Completed.

looks like timing is not used during simulation.
Please help me in isolating the problem

http://www.edaboard.com/thread299176.html