In the context of IBM Watson, what is a 'dialog node' used for?

A dialog node in IBM Watson is primarily used to manage conversation flow within a chatbot or virtual assistant. It serves as a fundamental building block for defining how the system responds to user inputs and dictates the progression of the conversation. Each dialog node can be configured with specific conditions for when it should be triggered, along with the appropriate responses or actions for the system to take in response to the user's input.

In managing conversation flow, dialog nodes allow the designer to establish pathways that guide interactions logically and contextually. This facilitates a more coherent and engaging user experience by ensuring that responses are relevant to the previous exchanges. By utilizing various types of dialog nodes, such as those for conditions, responses, or actions, developers can create complex conversational scenarios that adapt to user behavior and preferences.

The other options do not accurately describe the function of a dialog node. User authentication is typically managed through different security protocols, storing user data would usually involve databases or data management practices, and deploying machine learning models involves a separate set of processes and tools in the AI lifecycle. Thus, managing conversation flow is the key role of a dialog node within the IBM Watson framework.