association between actor and use case are indicate in use case diagram by solid line .an association exit whenever an actor is involved with an interaction described by use case.association are modeled as lines connection use case and actor to one another,with an optional arrowhead on one end one another ,the arrowhead is often used to indicating the direction of the initial invocation of there relationship or to indicate the primary actor within the use case.the arrowhead are typically confused with data flow and use case.