Final answer:
Yes, a separate use case can be used as part of the workflow in an activity diagram, which helps in connecting high-level business processes with the workflow in a system.
Step-by-step explanation:
In an activity diagram, a separate use case can indeed be incorporated as part of the workflow. This is because activity diagrams are used for modeling dynamic aspects of a system and are designed to show the flow of control or data from activity to activity. Integrating a use case can help in providing a more comprehensive representation of the system by connecting high-level business processes with the more detailed workflow. However, it is important to maintain clarity in the diagram to ensure that the connection between the use case and the workflow is understood clearly by all stakeholders.