Z:gnu-www-ja-free-encyclopedia--49eca6-Courses must evolve, and the o/en

Courses must evolve, and the original authors won't keep working on them forever. And teachers will want to adapt course materials to their own curriculum plans and teaching methods. Since courses will typically be large (like a textbook today), it would be unacceptably wasteful to tell teachers, &ldquo;Write your own from scratch, if you want to change this&rdquo;.