Fig 3. Three types of update to the graphical model.
Delete denotes unlinking an existing link, reverse denotes reversing an existing link, and join denotes creating a new link.
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.