In his new book "The Semantic Turn -- a new foundation for design" Klaus Krippendorff presents a new understanding of design. I am still reading the book but I am already sure that this is one of the best theoretical books on design today. The author is consistent in his perspective based in language. He convincingly argues for a turn to the meaning of designs. This turn is in his perspective a semantic turn. Design as a meaning making process.
It is fascinating to see the way Krippendorff comes to so many conclusions on the nature of design that are similar to what I together with Harold Nelson present in our book "The Design Way--intentional change in an unpredictable world", even though we come from very different backgrounds and perspectives.
I am quite convinced that we are slowly seeing a new and foundational understanding of design develop and grow into existence. Our own book, the new book by Krippendorff, the books by Donald Schon, and some others, are in a way all converging in a promising way. I think we are entering the time when design will in a serious way develop its own theoretical and philosophical foundation. There are of course many differences and controversies but the overall intention and aim is that design is its own tradition, fully worthy and in need of a theoretical and philosophical treatment that parallels our other major intellectual traditions, such as science and art. It is a promising development!