how to send only one parameter from parent interface to child

hi, 

I have a child interface , that has a rule input just to update the data base. I am basically trying to select the rows from an editable grid and save them in this rule input which is not dependent on parent interface. it is handled internally in child interface. 

Child interface rule inputs - ri!id and ri!selectedrows

I am trying to configure this interface in the Landing Page ( Parent Interface ) , now from parent interface I wanted to pass only the id. how do I achieve it .

I get an error, if I pass only id from parent .