UMLR — Location: Pg. 613, Figure 17.6 - : Incorrect multiplicities in the metamodel in Figure 17.6

The multiplicity shown for “coveredBy : InteractionFragment” is “”. However, I believe the lower multiplicity should be 1, not 0. A lifeline can only exist within an Interaction; it cannot exist independently. This is affirmed by the multiplicity of “1” shown in this figure for the end “interaction : Interaction”. And an Interaction is a type of InteractionFragment as we see in the metamodel in Figure 17.1. Therefore, an instance of Lifeline must always know at least one instance of InteractionFragment: the Interaction that owns it. And thus, the multiplicity for “coveredBy : InteractionFragment” should be “1..”, not “*”.

Proposed Resolution:
Change the multiplicity for the end “coveredBy : InteractionFragment” to “1..*”