Please create use cases for each of the actors for the following software system:

Fitness Tracker: A fitness tracker is a software system that allows users to track their physical activity, diet, and health data. This system would have four actors: the user, the fitness tracker, the health data source, and the database. The user would input their physical activity, diet, and health data into the system, which would be tracked by the fitness tracker. The health data source would provide data such as heart rate, sleep patterns, and other health metrics. The database would store and manage the user's data, and the system would provide the user with personalized recommendations based on their data.