Probably the most widely known teachings of backward design are from the book Understanding by Design by Grant Wiggins and Jay McTighe. Although based on the same components as the ADDIE model, it deserves separate distinction. Backward design begins by thinking of the end in mind. What do I want students to understand and know? What would be acceptable evidence that students do understand and know? Then instructional activities and assessments can begin. Understanding by design (UbD) is a set of tools for making you ultimately more productive when creating backward design. As Wiggins and McTighe point out, "Good design, then, is not so much about gaining a few new technical skills as it is about learning to be more thoughtful and specific about our purposes and what they imply."