One of the benefits of these types of diagrams is that every line coming from an actor that represents a person, tells you that something in your UI has to provide a capability needed by that person.
Moja ya faida ya aina hii ya vielelezo ni kwamba kila mstari kuja kutoka muigizaji kwamba inawakilisha mtu, atakwambia kwamba kitu katika UI yako ina kutoa uwezo zinahitajika kwa mtu huyo.