Not every module contributes to every element.

Each process, or "runtime", applies different constraints to the code that runs in that process.
For example, each process has different supported JVMs and a different set of services available for dependency injection.
While a lot of Gradle source code runs only in the Gradle daemon, not all of it does and so, when working on some source code it is important to be aware of the runtimes in which it will run.

- Some base services that are available to code hosted by the runtime. This varies by runtime.
- Additional constraints. For example, the CLI client runtimes limit the libraries that are available to the code in that runtime, for performance reasons. 

Other modules and platforms define the services that they contribute to the runtime.