W3 address syntax: BNF

This is a BNF-like description of the W3 addressing syntax . We use a vertical line "|" to indicate alternatives, and [brackets] to indicate optional parts. Spaces are representational only: no spaces are actually allowed within a W3 address. Single letters stand for single letters. All words of more than one letter below are entites described elsewhere in the syntax description. (Entity names are here linked to their definitions, probably making this difficult to read with the line mode browser.)

An absolute address specified in a link is an anchoraddress . The address which is passed to a server is a docaddress .

anchoraddress: docaddress [ # anchor ]
docaddress: httpaddress | fileaddress | newsaddress | telnetaddress | prosperoaddress | gopheraddress | waisaddress
httpaddress: h t t p : / / hostport [ / path ] [ ? search ]
prosperoaddress: p r o s p e r o : / / hostport / path
fileaddress: f i l e : / / host / path
newsaddress: n e w s : groupart
waisaddress: waisindex | waisdoc
waisindex: w a i s : / / hostport / database [ ? search ]
waisdoc: w a i s : / / hostport / database / wtype / digits / path
groupart: * | group | article
group: ialpha [ . group ]
article: xalphas @ host
database: xalphas
wtype: xalphas
telnetaddress: t e l n e t : / / [ user @ ] hostport
gopheraddress: g o p h e r : / / hostport [/ gtype [ / selector ] ] [ ? search ]
hostport: host [ : port ]
host: hostname | hostnumber
hostname: ialpha [ . hostname ]
hostnumber: digits . digits . digits . digits
port: digits
selector: path
path: void | xalphas [ / path ]
search: xalphas [ + search ]
user: xalphas
anchor: xalphas
gtype: xalpha
xalpha: alpha | $ | _ | @ | ! | % | ^ | & | * | ( | ) | . | digit
xalphas: xalpha [ xalphas ]
ialpha: alpha [ xalphas ]
alpha: a | b | c | d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
digit: 0 |1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
digits: digit [ digits ]
alphanum: alpha | digit
alphanums: alphanum [ alphanums ]
void

See also: General description of this syntax, Escaping conventions. _________________________________________________________________

Tim BL