search for: xsurnamegoodall

Hallo, I'm new to xapian and have only started checking it out, so please forgive my silly questions. I'm trying to get my head around the following: Given the following fields (values with prefixes): Name: .... Surname: .... Address: .... ... How can I (by default) search in Name and Surname only? ie, I want to ignore the Address field during search, unless I explicitly search it