Anchor: A joke sets up a chain of logic, and then subverts it in a surprising and delightful way; that's the punch line.
Entailed: A good joke sets up a chain of logic.
Contradiction: A joke is generally defined as following no chain of logic and ending in a predictable way.
Contradiction: People jumping off the bridge
Contradiction: The man is walking a bike.
Contradiction: Jet lag and insomnia are myths perpetrated by the sleep industry. 
Contradiction: There was a discussion about  Congress' object and purpose.