An e-learning course may include a number of structural elements that are aggregated into one or more levels. Each higher level may refer to any instance of a lower level. The structural elements include a course, a sub-course, a learning unit, or a knowledge item. The structural elements may include metadata. The structural elements also may include relations between structural elements. The course and its structural elements do not enforce any sequence of structural elements that the learner may use to traverse the course. In addition, the structural elements may be reused and reassembled to form different courses. A content repository is configured to store course data and its structural elements. A content player is configured to access the stored course data and assemble the structural elements.