Accuracy, Robustness, Security, & Redundancy
In the design of an authentication system (i.e. electronic door lock & payment verification) or other information system, there are 4 things to concern.
The system must allow the right person to get access and disallow the others. For example, if the twins can get access using a facial recognition, the system has low accuracy. The system must not allow the use of photocopy or fake fingerprint.
The system must be strong against disturbance. For example, if the user has changed the hair style or makeup, the system must still recognize and allow the right person.
The system must prevent illegal access such as hacking.
Redundancy is the way you assign the same job to different people or systems. This word can be both positive and negative.
Example 1: You let Mr. A works on task 1 and 2, and Mr. B works on 2 and 3. Both of them achieve similar results on task 2. You choose one and discard the other. This is a "negative" redundancy. You pay more, waste more time and manpower without any improvement.
Example 2: A commercial bank provides different methods of financial transactions; mobile app, ATM, and counter. If the mobile app doesn't work, there are still two more channels available. This is a "positive" redundancy.Your goal is to "reduce negative redundancy" while "maintain positive redundancy".