Co-Director, Ruby Central, Inc.David A. Black is a long-time Ruby and Rails programmer, author, and trainer. Active in the Ruby world since 2000, David is the author of Ruby for Rails: Ruby techniques for Rails developers, from Manning Publications. He has co-organized numerous Ruby/Rails conferences and spoken at conferences and Ruby/Rails users groups in the United States, Canada, and England. David is the chief author of Ruby's standard scanf library, and the author and maintainer of the official Ruby Change Request site.