Perhaps the different Jedi "sub-groups" are entire cohesive orders of individuals who have some ideological splits between each other but are all united by a few common principles of "Jedi-ness", they just differ in how they interpret the Force. We see a small glimpse of this in the differences in the descriptions of the Force given to Luke by Obi-Wan and Yoda in ANH and ESB respectively.

Basically, under the large over-arching designation of JEDI, there are various clans that operate autonomously. These are "the Knights", "the Masters", "the Navigators", or what-have-you.