Defining Operating Condition in PD using EDI

I want to introduce operating conditions into the flow.
 Here are my questions?
1). How these operating conditions are defined?
2). Is it dependent on Synthesis and Rtl?
3). On what basis these operating conditions are decided?
4). What is difference between prePD and postPD netlist?

Answers:
1). Using setOptCond command.
2). No.
3). Normally best case and worst case operating conditions is used for EDI do timing optimization          for setup and hold.
4). postPD netlist has complete clock tree structure ans so more accurate timing analysis with wire          capacitance.