Forward compatibility
（重定向自Upward Compatibility）
Forward compatibility is a design characteristic that allows a system to gracefully accept input intended for a later version of itself. The concept can be applied to entire systems, electrical interfaces, telecommunication signals, data communication protocols, file formats, and computer programming languages. A standard supports forward compatibility if a product that complies with earlier versions can "gracefully" process input designed for later versions of the standard. Although the ability of a system to select known input and ignore unknown input also depends on whether the new standard is backward compatible.