A simple sum of selected individual agent performance on a role is a good way to express team performance because it provides a basic measurement of how well each agent is fulfilling their assigned role in the collaboration. By summing up the individual performance values, we can get an aggregate value that reflects the overall performance of the team as a whole. This approach is particularly useful when the task can be easily divided into individual tasks and the performance of each task is well defined and measurable. Additionally, this approach is easy to understand and implement, making it a simple and effective way to express team performance in many cases. However, for more complex systems that are difficult to divide into clear tasks, it may be necessary to add constraints and make adjustments to the simple sum to accurately reflect the team's performance.
In RBC, GRA (Group Role Assignment), as a basic form of role assignment, has limitations in dealing with complex systems where the tasks are not easily divided. In such cases, GRA+ (Group Role Assignment with Constraints) and GRA++ (GRA with Multiple Objectives) can be used to account for constraints and adjust the team performance accordingly.