DRAT System (2006)

from What it is About:

One of the primary goals of the DRAT System is to create a role-playing system that facilitates systems and settings that do not translate well to traditional role-playing systems. That is to say, settings like Star Trek have elements which are inconsistent. Traditional RPGs often functions best in consistent set of setting presumptions. If a players fires his phaser at a ship and it is powerful enough to destroy it then he will reasonably expect it to happen every time he fires at a ship. However, in many stories there are exceptions that move the story forward.

To resolve this we need to look to cooperative role-playing systems. In this manner, a group of like minded people can use such a system to explore settings that do not follow a predictable set of rules. Plot exceptions can be agreed upon by the Group and not become a point of disruption in a game but rather an event to drive the story forward.

from DRAT System:
DRAT System stands for Dice-less Role-playing And Tactics System. The goal of this system is to provide the tools for a cooperative storytelling experience. If everyone in the group is not committed to telling a story, the game will not work. To that end, make sure that all members of the group are aware and willing to participate in telling the story as well as describing their character’s action.

These rules are available as a free download.