Rewrite Rule

重写规则

A type of rule in generative grammar, which takes the form X → Y; also called a rewriting rule. The symbol to the left of the arrow represents a single structural element; the symbol to the right of the arrow represents a string of one or more elements: and the arrow is an instruction to replace (or ‘expand’) X by Y. Such rules are conventionally read as ‘Rewrite X as Y’.

生成语法的一类规则，形式为X→Y。箭头左边的符号代表单一的组构成分；箭头右边的符号代表一个或多个部分的语符列；箭头指示用Y取代（或“扩展”）X。这类规则习惯上读作“重写X为Y”。