Hi Vignesh,
Thank you for reply 
We want to update attribute value and it is not maintained in any lookup field these values are maintained at taxonomy table level. I have heard of branch assignments which can help me in this but when I tried using I am not able to run the child assignment. Can you please help me with an example or any doc that can help me to write a branch assignment.
About calculated fields can u please elaborate how it can be achieved ?
Regards,
PB