descriptions but seldom documented anywhere, so that it must
usually be learned by osmosis from other hackers. Consider this
BNF for a U.S. postal address:

::=

::= | "."

::= []
|

::= []

::= ","

This translates into English as: "A postal-address consists of a
name-part, followed by a street-address part, followed by a
zip-code part. A personal-part consists of either a first name or
an initial followed by a dot. A name-part consists of either: a
personal-part followed by a last name followed by an optional
`jr-part' (Jr., Sr., or dynastic number) and end-of-line, or a
personal part followed by a name part (this rule illustrates the
use of recursion in BNFs, covering the case of people who use
multiple first and middle names and/or initials). A street address
consists of an optional apartment specifier, followed by a street
number, followed by a street name. A zip-part consists of a
town-name, followed by a comma, followed by a state code, followed
by a ZIP-code followed by an end-of-line." Note that many things
(such as the format of a personal-part, apartment specifier, or
ZIP-code) are left unspecified. These are presumed to be obvious