URI = scheme ":" hier-part [ "?" query ] [ "#" fragment ]

hier-part = "//" authority path-abempty / path-absolute / path-rootless / path-empty

URI-reference = URI / relative-ref

absolute-URI = scheme ":" hier-part [ "?" query ]

relative-ref = relative-part [ "?" query ] [ "#" fragment ]

relative-part = "//" authority path-abempty / path-absolute / path-noscheme / path-empty

scheme = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )

authority = [ userinfo "@" ] host [ ":" port ]

userinfo = *( unreserved / pct-encoded / sub-delims / ":" )

host = IP-literal / IPv4address / reg-name

port = *DIGIT

IP-literal = "[" ( IPv6address / IPvFuture ) "]"

IPvFuture = "v" 1*HEXDIG "." 1*( unreserved / sub-delims / ":" )

IPv6address = 6( h16 ":" ) ls32

/ "::" 5( h16 ":" ) ls32

/ [ h16 ] "::" 4( h16 ":" ) ls32

/ [ *1( h16 ":" ) h16 ] "::" 3( h16 ":" ) ls32

/ [ *2( h16 ":" ) h16 ] "::" 2( h16 ":" ) ls32

/ [ *3( h16 ":" ) h16 ] "::" h16 ":" ls32

/ [ *4( h16 ":" ) h16 ] "::" ls32

/ [ *5( h16 ":" ) h16 ] "::" h16

/ [ *6( h16 ":" ) h16 ] "::"

h16 = 1*4HEXDIG

ls32 = ( h16 ":" h16 ) / IPv4address

IPv4address = dec-octet "." dec-octet "." dec-octet "." dec-octet

dec-octet = DIGIT ; 0-9

/ %x31-39 DIGIT ; 10-99

/ "1" 2DIGIT ; 100-199

/ "2" %x30-34 DIGIT ; 200-249

/ "25" %x30-35 ; 250-255

reg-name = *( unreserved / pct-encoded / sub-delims )

path = path-abempty ; begins with "/" or is empty

/ path-absolute ; begins with "/" but not "//"

/ path-noscheme ; begins with a non-colon segment

/ path-rootless ; begins with a segment

/ path-empty ; zero characters

path-abempty = *( "/" segment )

path-absolute = "/" [ segment-nz *( "/" segment ) ]

path-noscheme = segment-nz-nc *( "/" segment )

path-rootless = segment-nz *( "/" segment )

path-empty = 0<pchar>

segment = *pchar

segment-nz = 1*pchar

segment-nz-nc = 1*( unreserved / pct-encoded / sub-delims / "@" )

; non-zero-length segment without any colon ":"

pchar = unreserved / pct-encoded / sub-delims / ":" / "@"

query = *( pchar / "/" / "?" )

fragment = *( pchar / "/" / "?" )

pct-encoded = "%" HEXDIG HEXDIG

unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"

reserved = gen-delims / sub-delims

gen-delims = ":" / "/" / "?" / "#" / "[" / "]" / "@"

sub-delims = "!" / "$" / "&" / "'" / "(" / ")" / "*" / "+" / "," / ";" / "="