Ralph Johnson is one of the four co-authors of Design Patterns, co-author of the first paper to use the word "refactoring" and leader of the group that developed the first automated refactoring tool, the Smalltalk Refactoring Browser. He recently retired from the University of Illinois, and is now with Metaficient, a company making an end-user programming system for accountants.
The book "Design Patterns" was released in October of 1994 and is still in print. It has received many awards and has many imitators. However, the years have shown weaknesses in the book. This talk describes a few lessons that we have learned since writing it.