This image is attributed to Ed Yourdon © 2009 (CC-BY-SA 2.0)

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012

This image is being used with the permission of Corey Nasfell © 2012