The L6 – Logical Sequence viewpoint of NAF v4 is a diagram that enables you to view Roles (Performer PerformsInContext Activity) as vertical lifelines, and the OperationalExchanges sent between the Roles as relationship lines between them. This is a UML Sequence type diagram, used for NAF v4.
The top-to-bottom positioning of the OperationalExchange lines denotes the timing of which OperationalExchange happens first to last (top to bottom).