| "^" | "_"
word ::== atom | quoted-string
quoted-string ::== '"' (qtext | qpair) *endq"
qtext ::== (^'"')["\"]
endq ::== [^"\\"]
space ::== *(" ")
qpair ::== "\\."
shortcode-address ::== shortcode-string
shortcode-string ::== *(ALPHA | DIGIT | "!" | '"' | "$" | "%" | "&"
| "/" | "(" | ")" | "+" | "*" | "." | "-"
| "/" | "=" | "< | ">" | "[" | "]" | "_"
| "^" | "?" | "{" | "}" | "'" | "~" | ";"
applicationID-symbol ::== ALPHA | DIGIT | "." | "_"
例子: