You are designing a system where objects need to be composed…

You are designing a system where objects need to be composed into tree structures to represent part-whole hierarchies (e.g., a file system with folders and files). Both individual objects and groups of objects should be treated uniformly. Which pattern is most appropriate?

Consider an e-commerce application’s order processing pipeli…

Consider an e-commerce application’s order processing pipeline. An order must first pass a validation check, then an inventory check, and finally a fraud check. If any check fails, the process stops. If it passes, it is sent to the next handler. This represents a loosely coupled sequence of processing objects. Which pattern is designed for this scenario?