We propose in this paper a new method to compute indicators based on models transformations. We use the concept of modeled trace and trace-based system to design an indicator. We use traces transformations to build indicators model and to actually compute them. Effective implementation of the indicator is demonstrated through the transformations effected on a particular learning platform based on real traces, constituting so called primary modeled traces. A «path» of transformations is

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... y designed and applied both for documenting and building the indicator. We illustrate our approach on the Moodle learning platform through a concrete example describing a practical use of our contribution.