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