The functional programming language Erlang is rightfully touted by its supporters as being fault-tolerant. COSA shares all the fault tolerance qualities of Erlang but this is where the similarities end. The COSA philosophy is that nothing should fail, period. There are software applications where safety is so critical that not even extreme reliability is good enough. In such cases, unless a program is guaranteed 100% reliable, it must be considered defective and should not be deployed. That's the main goal of project COSA: 100% reliability, guaranteed.