Thanks for the pointer to VSM, I've not come across that before! I will probably update the essay at some point when I've had more feedback and started playing

Thanks for the pointer to VSM, I've not come across that before! I will probably update the essay at some point when I've had more feedback and started playing around with the ideas more. As for the other mentioned models, I mainly just wanted to define their factors so I could show how WOPRS relates to these models, rather than providing a thorough treatment of those models in my essay: there is plenty already written about them and I've included some authoritative sources in the references. :)