Abstract: "Design Patterns", by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, was released in October, 1994. It has continued to sell for 20 years and has had a big impact. Twenty years after it came out, some of the patterns continue to be important, some less important. New patterns have arisen that have displaced some of the older patterns. There are common ways that the patterns are misused. Ralph Johnson will talk about what he has learned about the patterns since the book was published.
Biography: Ralph Johnson is one of four coauthors of "Design Patterns" and the leader of the group that built the first refactoring tool, the Smalltalk Refactoring Browser. He is still working on patterns and program transformation, though the spotlight has shifted off of basic object-oriented design to topics like parallel programming and innovative ways of making business software. He joined the Department of Computer Science at the University of Illinois at Urbana-Champaign in 1985, and retired recently to work on a system for automating business transactions.