Stimulus: The product team provides a new feature.
Reaction: The system updates itself in a way that the new feature can be used.
Metric: There is no action required from the user to be able to use the new feature, i.e. the new feature just becomes available.
Background: If software is provided via an install kit, it may need to be provided for different operating systems and users will have to run an update installer to access new features. In contrast, web-based systems retrieve their logic over the network, so no action from the user site is needed. Since a requirement, like the one above, is not dictating a solution, but what needs to be fulfilled other solutions than a web-based system that avoids installation were also valid.