Greenhouse effect

What kind of models are represented and what is their role? Norman's differentiation of models where a difference is made between mental models of learners and the conceptual models of recearchers and scientist of the system, and also between recearcher's conceptualization and learner's mental models. Hypermodels is a model realized via computer. Learner interacts with external with interactive curricula. During this interaction constructs and/or revises his mental model. Representation are considered effective only if they favor the learning and understanding of the target model. Metacognition is also considered as an important theorie.