Classification of models.

[roodborst]

I was wondering on what basis the classification of origami models is made. When is a model beginner level or intermediate or complex?

[Flame_Kurosei]

Classification differs from book to book, person to person. Of course, there is a major difference between a traditional crane and an Ancient Dragon, but the exact science of the classification is grey.
However, some explain their reasoning for associating certain models with certain difficulties, such as OUSA:
http://origamiusa.org/difficulty
(I'm not saying I agree with this view, it's an example.)

[roodborst]

This was helpfull. The way I understand it now is that it depends on the amount of explaining done in the diagrams and difficulty of the folds. I was wondering because I just made a guinea pig by Chad Kileen, wich stated that it was a complex model, but it only had one hard sink and two more sinks that where actually straightforward. But using the guidelines stated in the link those sinks would make the model 'complex'.

For me the more accurate the diagrams are the easier the model. You can have a 150 step model that you can do easily because the diagrams are clear and struggle on a lesser step model because you mist something. I think it is one of Kamiya's strenghts, his models are complex but makes very good diagrams. I've had a harder time folding some stuff of Diaz, he tends to do multiple things in one picture so have to be very alert when folding to see what the changes are between pictures.