Primetime timing analysis Error: No timing arc in cell from to

After I synthesized in design compiler, I write_milkyway to store my design.
Then I read_milkyway in Primetime, after read milkyway, when I report_timing, I should get the timing report show all the pints in critical path are annotated, but I didn't get it, all the points don't have * to show they are annotated, I don't know why...

In prime time, I used to set_annotated_delay to annotate some cells rise delay, but I only can annotate delay belong to IVX4, BFX4,BFX9.... all the others cell like NAND2X3, NOR2X2,NAND3X5... all of them cannot be annotated!
I got the warning: The timing arc (0->1,0->Z,Z->1)of cell 'u3_control/U57' from 'B' to 'Z' could not be annotated.(SDF-019)
Error: No timing arc in cell 'u3_control/U57(HS45_LS_NOR3X2)' from pin 'B' to 'Z'.(PTE-008)
....
...
all of the cell from nand, nor,and or has same problem, but inv don't have this problem. I don't why..
And in SDF file, I can find all the timing information of them, but primetime has error..
Anybody can bring some idea of the potential mistake?

What is timing arc when uses primetime.

Hi guys,
Since I met an error when I annotate rising delay from one cell input pin to output pin. But i got the error : no timing arc between such two pins.
The error is :
Error: No timing arc in cell 'u3_control/U57(HS45_LS_NOR3X2)' from pin 'B' to 'Z'.(PTE-008)

So I want to understand what is the timing arc? I write the milkway in design compiler, and read it in primetime, but I got this problem....

Thanks anyway if you could provide any ideas about this.

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The command I used in Prime Time is set_annotated_delay

set_annotated_delay -cell -rise -increment -from -to