Robustness principle - Wikipedia

In computing, the robustness principle is a design guideline for software: Be conservative in what you do, be liberal in what you accept from others (often reworded as "Be conservative in what you send, be liberal in what you accept"). The principle is also known as Postel's law, after Jon Postel, who wrote in an early specification of TCP: TCP implementations should follow a general principle of robustness: be conservative in what you do, be liberal in what you accept from others.