In my opinion the Doyle UPS is not a spinnaker because it is not a downwind sail; it is a drifter/reacher. However, racing rules and measurement commitees have ruled that it is indeed a spinnaker. I can only conjecture that it has something to do with the lack of hanks, though the old drifter-reachers didn't have hanks and weren't spinnakers.
http://en.wikipedia.org/wiki/Spinnaker has a fairly thorough overview. Here is the gist:
Code 0 The code 0 asymmetric is a tight reaching sail, the most upwind capable of the asymmetrics. The luff is as straight as possible, and the sail is flatter than other spinnakers. Due to the flatness of the code 0, it is usually made with a wire luff for strength, and of a heavier, less stretchy fabric than normal for a spinnaker. Due to the tight luff and flat cut, the code 0 can be fitted for roller furling.
Code 1 The code 1 is a light air reaching sail, where the apparent wind angles at low speeds has a significant effect to create angles of less than 90 degrees.
Code 2 The code 2 is a medium air running sail, used for apparent wind angles over 90 degrees.
Code 3 The code 3 is a medium air reaching sail, used for apparent wind angles near 90 degrees.
Code 4 The code 4 is a heavy air running sail, used in the heaviest winds normally expected.
Code 5 The code 5 is a heavy air reaching sail, used in the heaviest winds normally expected.
Code 6 The code 6 is a storm sail, for running in storm conditions.