This is a generic intermediary format for sampler instruments. It is useful for conversion between the many sampler formats out there. Essentially it means you only need to write a single conversion to and from this schema and you can now export it into any of the other formats supported by this interface, use it in any sampler that supports this generic format, or serialize it to disk as-is.
This project is part of the Open Sound Project, a wider effort to open source proprietary audio formats and free the audio industry from proprietary vendor lockin.