Final answer:
Asynchronous message invocation is represented in sequence diagrams, which illustrate the flow of messages over time in UML.
Step-by-step explanation:
Asynchronous message invocation can be expressed in a sequence diagram. Sequence diagrams, which are a part of Unified Modeling Language (UML), are used for representing the sequence of messages between objects in a time-ordered fashion. Asynchronous messages, which are a type of communication where the sender does not wait for a response before continuing execution, are depicted with an open arrow and without a return message, distinguishing them from synchronous messages which require a response before the sender continues.