A whole classification process is the result of a discovery process that requires constant back and forth between theoretical description of the solution, software implementation, testing and refinement of the theoretical description in the light of the results of experimentation. This process is iterative. It should be, always, under the control of the user according to his subjectivity, his knowledge and the purpose of his analysis. In the last years, several platforms for digging data where classification is the main functionality have emerged. Some of these platforms allow a rapid prototyping and support a re-use of existing “computational modules” from existing “computational tool cases”. However, they lack flexibility and sound formal foundations. We propose, in this paper, a formal model with strong logical foundations, based on typed applicative systems. In this model, “computational modules” are considered as operators followed by their operands. A specific processing chain becomes a specific arrangement of a set of modules according to the needs of the user. The model ensures a firm compositionality of this arrangement.