[Names] boolean-is-in [Result] True iff the first argument is equal to one of the attribute values in the bag of the second argument (according to the "boolean-equal" predicate). [Arguments] 
An attribute value of http://www.w3.org/2001/XMLSchema#boolean as the first argument, and a bag of attribute values of http://www.w3.org/2001/XMLSchema#boolean as the second argument