Learning a second language (L2) is a complex process made up of acquisitional stages. These stages correspond to phases of development in which the language of the learner shows specific features forming a separate language system, i.e. Interlanguage or IL (Selinker, 1972). These features can be grouped in three main classes, i.e. Complexity, Accuracy and Fluency (Bulté & Housen, 2012). With a view to transform language teaching methods and to develop Computer-aided Language Learning (CALL) systems, it is essential to identify the combinations of CAF features that are significant in the description of performance. It is equally important to identify features that can be used for meaningful language description (Biber et al., 2020).