Interaction Diagrams

The sequence and collaboration diagrams represent
the interactions between objects. As such, they are
valuable tools for identifying object interfaces.
Interfaces in turn help identify the attributes that
must be supported by the class diagram. Attributes
contain data values. Data values are passed as
arguments and return values in interfaces. A value
cannot be passed as an argument if it is not contained
in an attribute on some object or created by an
operation that belongs to an object (a derived
attribute).