Constraints:

• Every single procedure and function checks the sanity of its arguments and either returns something sensible when the arguments are unreasonable or assigns them reasonable values

• All code blocks check for possible errors and escape the block when things go wrong, setting the state to something reasonable

Possible names:

• Constructive
• Defensive
• Hopeful
• Shit happens, life goes on

(See http://en.wikipedia.org/wiki/Constructivism_(mathematics))