This vocabulary is based on decades of work in academia and some limited work in the field in software implementations - and further development by the VF team through documenting and studying use cases. The stability of the model reflects this history. The core model is fairly stable, more so in structure, somewhat less in naming. However, there are many edge cases and possibly not-so-edge cases where the model will need to be adjusted for the reality in the field based on further experience. Also, this model represents something new, something that we want to be able to support the next economy, with all the unknowns that will bring.