在学语言学时，碰到一个问题不是非常理解，望各位老师解答。非常感谢！
A grammar which consists of a set of statements or rules which specify
which sequences of language are possible, and which impossible, is a generative
grammar.
请问为什么是generative grammar而不是prescribtive grammar呢？这二者有什么联系和区别呢？
