UDL - Universal Design for Learning

What is the difference between Universal Design for Learning (UDL) and Differentiated Instruction (DI)?  In this  explanation it appears that UDL often empowers the learner than relying on the modifications by the teacher.

"The significant differences between UDL and DI tend to dwell within the world of the how and when in addressing the diversity of the student and classroom. DI is the modification of the curriculum in order to properly educate the student with his/her specific learning needs or preferences. UDL contrasts this because it addresses the diversity of the student at the construction of the curriculum. UDL also integrates the methods for DI within the lesson or curriculum allowing the student the ability to become more educationally aware so that they are in command of their own education rather than having to rely on the possible crutch of the modifications made by the educator."

Aaron Puley provides a set of links to a wealth of resources that can support assessment, differentiated instruction and the principles of Univeral Design for Learning.