This is fantastic! Formerly trained as a horticulturist, I've been thinking about how I could explain PKM's fit in the organization through a model that other science educators might relate to, such as the disease triangle (http://www.apsnet.org/edcenter/instcomm/TeachingArticles/Pages/DiseaseTriangle.aspx) or soils triangle (http://en.wikipedia.org/wiki/Soil_texture), but neither seemed to fit exactly. This does it ever so simply and to the point. I can't wait to share this with others.