caculate the diff data in pydatalog

[Gao Zhenyu]

Hi all

   I wonder to know if we can have a way to tell pydatalog to only caculate the diff data entries.

   You know, we may have numerous data, it cost so much time if we have to caculate it each time.
   So I want to know if we have a way to caculate the diff data? Like you add some entry, and you get the final result that was affect by those added entry.

   switch_port(X, Y) <= (switch(X) & port(Y, X))

   +switch("A-switch")
   +switch("B-switch")
   +port("A-port", "A-switch")
   ====================
    set_snapshop_here

    +port("B-port", "B-switch")

     Then switch_port(X, Y)  only output "B-port" "B-switch", because B-port is the new entry, and it trigger the clause.

      So I want to know if we have a way to reduce the caculation in each time.


Thanks
Zhenyu gao