The digital transformation of organizations, in the era of Industry 4.0, has profoundly renewed industrial work including design, production and distribution. With such an evolution, actors would learn a lot and redefine many formal (operating methods, procedures, processes, methods) and informal (corrections/remedies, local regulations, skills, etc.) working practices. Competencies are at the heart of these learnings and practices. Sociologists, psychologists, ergonomists and engineers have tried to define and characterize "competency" for its better identification and evaluation. Most of these researchers agree that competencies are difficult to identify but could be determined by inferring them through observation and traceability of human actions-those being more or less representative of reality. However, this identification process requires upstream relevant competency modeling in order to better interpret the collected competencies' traces and then confront them with peers to access the judgment on competencies. The authors of this paper rely on a presentation of concepts from different disciplines to define competency, emphasize its link to action and propose an action-based competency model. An example observed in a Company is detailed to validate the proposed model. At the end of the paper, we identify six situational mechanisms of articulation between material, immaterial and the actor's personal resources, necessary for competencies deployment and construction.