[rules-users] A Simple Rule ( using Guided editor )

Hi All , I am just trying to write a simple rule but not sure how can i write it , Please help me as i am new to drools and still in the learning phase . I have a below Fact with three fields Person firstName lastName fullName Now i want to assign fullName = firstName + lastName which i am not able to find out how can i do that. I am able to define the *when *part using guided editor but able to define *then *part , Please help *rule "PersonRules" dialect "mvel" when p : Person( firstName != "" && lastName != "" ) then* Thanks, Ashish