Internet and mobile devices open the way towards mobile learning (m-learning), offering new opportunities to extend learning beyond the traditional teacher-led classroom. M-learning is not only any form of teaching or studying that takes place when the user interacts with a mobile device. It is more than just using a mobile device to access resources and communicate with others. It should take account of the constant mobile situation of the learner. The challenge here is to exploit this continually changing situation with a system that can dynamically recognize and adapt educational resources and services to the "context" in which the learner operates (localization, surrounding environment, learning time, goals, etc.). However, it is often difficult to identify relevant resources and to organize them into a coherent training course, especially when the learner context is continually changing. M-learning needs a better organization of knowledge, to deliver better in a mobile situation. A way to address this problem is to create a pedagogical repository of Learning Objects (LOs) and to model learner context. A semantic approach using ontologies provides a semantic organization of learning information and the personalized situation.