The FSF services and associated API are designed to be implementable inside any real-time operating system. It is also possible to implement them on top of an operating system that provides the ability to install application-level schedulers. There is currently no standard way of providing this kind of functionality, and therefore each FSF implementation would have to be tailored to a specific OS. To overcome this difficulty in the future, an API has been defined to specify services that allow an OS to provide application-level scheduling support in a uniform way, and we have started the process to request inclusion of this API into the real-time POSIX standard.