"GATE_TYPING_RULES" part in *.off file

Hi MS users,

I have a question . It is about the part named as "GATE_TYPING_RULES" in *.off file. I am using Perl script with MS libraries to write my own *.off file. if I compare my written *.off file with a standard FF like PCFF, I sea "GATE_TYPING_RULES" part is missed in my *.off file. "GATE_TYPING_RULES" part has a bit complicated procedure and is even hard to understand what it does. Could you make an example about "GATE_TYPING_RULES" procedure?

Regards,
Hamid