What integration mechanism allows for the exchange of messages between different systems?

The integration mechanism that facilitates the exchange of messages between different systems is messaging. This approach allows for asynchronous communication, where systems can send and receive messages without being tightly coupled to each other's processing states. Messaging is crucial in environments where systems need to operate independently and communicate efficiently, such as in service-oriented architectures or microservices.

By utilizing messaging, different applications can send messages containing relevant data or commands to one another, enabling them to perform operations in a decoupled way. This improves flexibility, scalability, and reliability, as systems can continue to function independently if one of them goes down or is undergoing maintenance.

While predefined plugins, web services, and startable plugins are important components in integration scenarios, they each serve different purposes. Predefined plugins are typically used to extend functionality within the system, web services provide a standardized way to interact using HTTP and API calls, and startable plugins enable certain operations to begin or trigger events. However, none of these options inherently focus on the core ability to exchange messages between disparate systems as messaging does.