UMLR — Clarification of use case semantics

Use cases and associated sequence and activity diagrams are
widely used by systems engineers to specify the functionality of the system,
and describe the interaction between the system and the actors. However,
there is much confusion regarding use case semantics. Consider the following
recommendations to clarify use case semantics:
a) Establish an explicit representation to depict the relationship between a
use case and its realization as a sequence diagram, activity diagram, etc.
In addition, allow for a similar representation to show the relationship
between an included/extended use case, and the interaction fragments which
realize the included/extended use case.
b) Clarify the relationship between a use case (solid oval) and a
collaboration (dashed oval), and determine whether they can represent the
same or a similar concept.