Suitable Design pattern for multi module web application

I would like to know the best design pattern for handling multi module web application.

Example :- A REST web services project will handle different type of requests to send SMS.

Types of requests

1. Individual SMS trigger
2. Promotional SMS trigger
3. Interactive SMS trigger
4. Scheduled SMS trigger

there are different types of SMS to be sent and each type has its own business logic to be applied before triggering the SMS. which is the suitable design pattern to handle it?

Please provide your suggestion or links , it will be of great help for designing our project.