Hello Adrija Chakraborty,

To implement alert or notification messages in Mendix, especially for scenarios like a library management system, you'll typically utilize a combination of microflows, entities, and pages.

For the first scenario, where a member wants to receive a notification when their book request is approved, you can follow these steps:

1. Create an entity to store book requests, including fields for member ID, book ID, request status, etc.
2. Implement a microflow that checks for approved book requests for the logged-in member. This microflow can run periodically or triggered by certain events, such as a request status update.
3. If a book request is approved, send a notification message to the member. This notification message can be displayed on a dedicated page or sent via email or push notification. You can refer to the Mendix documentation on local notifications for implementing Local notifications: Local Notifications.

For the second scenario, where the librarian needs to send alert messages for overdue books:

1. Create an entity to store book loans, including fields for member ID, book ID, loan date, due date, etc.
2. Implement a microflow that checks for overdue book loans. This microflow can run periodically or triggered by certain events, such as a scheduled job or a user action.
3. If a book loan is overdue, send an alert message to the member or librarian. Similar to the first scenario, you can choose to display the alert on a dedicated page or send it via email or push notification.

These are simplified steps, and the actual implementation may vary depending on your specific requirements and the complexity of your Mendix application. As a beginner, I recommend exploring the Mendix documentation, tutorials, and training materials to get a better understanding of these concepts.

If you have any further questions or need assistance with specific aspects of your implementation, please feel free to ask!