HPF defines certain extrinsics such as HPF_LOCAL, and HPF_SERIAL as interfaces that HPFF believes are useful to the HPF community. But there are many more such extrinsic interfaces beyond those maintained by HPFF. HPFF has a adopted a policy of formally recognizing certain extrinsic interface definitions, where the interface, and its addition to the HPF document is considered to be a service to the HPF community. Examples are language bindings to HPF or library packages.