The fundamental unit of learning is an active transaction such as a question and answer.
If you think about how children learn once they have language, it begins with the child asking questions. “Daddy, what are stars?” “Mama, why do I have to eat my peas?” A child’s questions are the basic units of much verbal learning.
I think you could build a learning infrastructure with questions and answers. We can see models of this idea with “help” sections in software. These are still crude structures that need refinement, better navigation tools and better linking mechanisms, but this seems like a more appropriate infrastructure for learning.
Even if a “question and answer” structure is the right foundation for a learning infrastructure, there are still many problems to address in building such a structure. The biggest challenge is how to you provide answers to all the different levels of learners. Obviously, the question, “why is it light in the day time and not at night?” gets answered differently to a five-year old than a school-age child or a high school science student, yet the question can take the same form. A well-designed learning structure will need to adapt quickly to the level of interest and knowledge of the person seeking the knowledge. There will also need to be ways to put questions in context in order to provide meaningful answers.