求问header = [ element ] *( "," [ element ] ) 是什么语言写

Question

这是httpclient包里面的内容，
header = [ element ] *( "," [ element ] ) 是什么？用什么语言写的？麻烦解释一下前两句意思，有相关资料给出的话更好，谢谢

Some HTTP headers (such as the set-cookie header) have values that can be decomposed into multiple elements. Such headers must be in the following form:

header = [ element ] *( "," [ element ] )
element = name [ "=" [ value ] ] *( ";" [ param ] )
param = name [ "=" [ value ] ]

name = token
value = ( token | quoted-string )

token = 1*<any char except "=", ",", ";", <"> and
white space>
quoted-string = <"> *( text | quoted-char ) <">
text = any char except <">
quoted-char = "\" char

Answer 1

BNF表示法，语法规则跟正则差不多header = [ element ] *( "," [ element ] )header的格式为element开头，后面可以没有，或者有任意个 ，element也就是说 a 或者 a, b, c 这样的