The Internet has promoted several changes in the world, including on education. People have been more interested in learning, which makes developing higher quality content material even more important. In addition, people want to satisfy their learning needs according to their personal characteristics such as knowledge background and learning style. Therefore, nowadays there is a great interest on reusable learning content material and adaptive systems. Learning metadata standards contribute to achieve such reusability through the idea of learning objects. However, there is no guidance on how to develop learning objects, but only on how to describe them. The work presented in this paper proposes a model for structuring knowledge (concepts, demonstrations and interactions) in learning objects according to their context, representation and composition. This approach enables increased reusability and adaptability while providing better structured content material.