Which part of Appian architecture runs activities as outlined in process models?

The component of Appian architecture responsible for executing activities defined in process models is the Execution Engine. This part of the architecture handles the orchestration and management of workflows, ensuring that each step in a process model is executed as intended over its lifecycle.

The Execution Engine interprets the business logic outlined in the process models, triggers tasks, manages process instances, and coordinates the flow of execution. As processes may involve conditional paths, parallel execution, and other complex operations, the Execution Engine is essential for maintaining the integrity and performance of these operations.

In contrast, while the Application Server plays a key role in managing application resources and serving requests from users, it does not directly execute the activities of process models. The Analytics Engine focuses on processing data for reporting and analytics purposes, rather than executing workflow activities. The User Interface Layer is responsible for presenting data to users and capturing user interactions, but it does not run process models. Thus, the Execution Engine is the correct answer as it specifically pertains to the execution of activities in Appian process models.