Which step is NOT involved in creating an application in Appian?

The reason why the choice that involves setting an application prefix, choosing a data source, and configuring object security is not involved in creating an application in Appian lies in the specific roles and processes associated with application development within the platform.

When you create an application in Appian, you typically take steps that include naming the application, setting an application prefix, and configuring application security to ensure appropriate access levels for users and groups. This aligns with the actual foundational steps necessary to establish an application and lay the groundwork for its functionality and security.

Choosing a data source, while important for the overall functionality of the application and for data integration, is not a primary step in the application creation process itself. Instead, data sources are often configured later to connect various elements such as records, reports, and integrations to external systems or databases.

The other options focus on tasks that are essential in the creation or setup of an application, including securing the app at both the application and object levels, which contributes to a properly structured and secured application environment. Therefore, the inclusion of choosing a data source in that specific choice makes it the step not typically involved in the initial stages of application creation.