The rule to update the list item:
updateListItems('http://sparknit.com/sites/site_Name/list_name','11aaddb3-2ffc-4436-be1b-631e746fdcc3','<Query><Where><Eq><FieldRef Name="ID" /><Value Type="Counter" >1</Value></Eq></Where></Query>',['Name'],[getSiteCollectionUserID(PeoplePicker1)]);