rfc1738.txt

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3.7. NNTP

   The nntp URL scheme is an alternative method of referencing news
   articles, useful for specifying news articles from NNTP servers (RFC
   977).

   A nntp URL take the form:

      nntp://<host>:<port>/<newsgroup-name>/<article-number>

   where <host> and <port> are as described in Section 3.1. If :<port>
   is omitted, the port defaults to 119.

   The <newsgroup-name> is the name of the group, while the <article-
   number> is the numeric id of the article within that newsgroup.

   Note that while nntp: URLs specify a unique location for the article
   resource, most NNTP servers currently on the Internet today are
   configured only to allow access from local clients, and thus nntp
   URLs do not designate globally accessible resources. Thus, the news:
   form of URL is preferred as a way of identifying news articles.





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3.8. TELNET

   The Telnet URL scheme is used to designate interactive services that
   may be accessed by the Telnet protocol.

   A telnet URL takes the form:

       telnet://<user>:<password>@<host>:<port>/

   as specified in Section 3.1. The final "/" character may be omitted.
   If :<port> is omitted, the port defaults to 23.  The :<password> can
   be omitted, as well as the whole <user>:<password> part.

   This URL does not designate a data object, but rather an interactive
   service. Remote interactive services vary widely in the means by
   which they allow remote logins; in practice, the <user> and
   <password> supplied are advisory only: clients accessing a telnet URL
   merely advise the user of the suggested username and password.

3.9.  WAIS

   The WAIS URL scheme is used to designate WAIS databases, searches, or
   individual documents available from a WAIS database. WAIS is
   described in [7]. The WAIS protocol is described in RFC 1625 [17];
   Although the WAIS protocol is based on Z39.50-1988, the WAIS URL
   scheme is not intended for use with arbitrary Z39.50 services.

   A WAIS URL takes one of the following forms:

     wais://<host>:<port>/<database>
     wais://<host>:<port>/<database>?<search>
     wais://<host>:<port>/<database>/<wtype>/<wpath>

   where <host> and <port> are as described in Section 3.1. If :<port>
   is omitted, the port defaults to 210.  The first form designates a
   WAIS database that is available for searching. The second form
   designates a particular search.  <database> is the name of the WAIS
   database being queried.

   The third form designates a particular document within a WAIS
   database to be retrieved. In this form <wtype> is the WAIS
   designation of the type of the object. Many WAIS implementations
   require that a client know the "type" of an object prior to
   retrieval, the type being returned along with the internal object
   identifier in the search response.  The <wtype> is included in the
   URL in order to allow the client interpreting the URL adequate
   information to actually retrieve the document.




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   The <wpath> of a WAIS URL consists of the WAIS document-id, encoded
   as necessary using the method described in Section 2.2. The WAIS
   document-id should be treated opaquely; it may only be decomposed by
   the server that issued it.

3.10 FILES

   The file URL scheme is used to designate files accessible on a
   particular host computer. This scheme, unlike most other URL schemes,
   does not designate a resource that is universally accessible over the
   Internet.

   A file URL takes the form:

       file://<host>/<path>

   where <host> is the fully qualified domain name of the system on
   which the <path> is accessible, and <path> is a hierarchical
   directory path of the form <directory>/<directory>/.../<name>.

   For example, a VMS file

     DISK$USER:[MY.NOTES]NOTE123456.TXT

   might become

     <URL:file://vms.host.edu/disk$user/my/notes/note12345.txt>

   As a special case, <host> can be the string "localhost" or the empty
   string; this is interpreted as `the machine from which the URL is
   being interpreted'.

   The file URL scheme is unusual in that it does not specify an
   Internet protocol or access method for such files; as such, its
   utility in network protocols between hosts is limited.

3.11 PROSPERO

   The Prospero URL scheme is used to designate resources that are
   accessed via the Prospero Directory Service. The Prospero protocol is
   described elsewhere [14].

   A prospero URLs takes the form:

      prospero://<host>:<port>/<hsoname>;<field>=<value>

   where <host> and <port> are as described in Section 3.1. If :<port>
   is omitted, the port defaults to 1525. No username or password is



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   allowed.

   The <hsoname> is the host-specific object name in the Prospero
   protocol, suitably encoded.  This name is opaque and interpreted by
   the Prospero server.  The semicolon ";" is reserved and may not
   appear without quoting in the <hsoname>.

   Prospero URLs are interpreted by contacting a Prospero directory
   server on the specified host and port to determine appropriate access
   methods for a resource, which might themselves be represented as
   different URLs. External Prospero links are represented as URLs of
   the underlying access method and are not represented as Prospero
   URLs.

   Note that a slash "/" may appear in the <hsoname> without quoting and
   no significance may be assumed by the application.  Though slashes
   may indicate hierarchical structure on the server, such structure is
   not guaranteed. Note that many <hsoname>s begin with a slash, in
   which case the host or port will be followed by a double slash: the
   slash from the URL syntax, followed by the initial slash from the
   <hsoname>. (E.g., <URL:prospero://host.dom//pros/name> designates a
   <hsoname> of "/pros/name".)

   In addition, after the <hsoname>, optional fields and values
   associated with a Prospero link may be specified as part of the URL.
   When present, each field/value pair is separated from each other and
   from the rest of the URL by a ";" (semicolon).  The name of the field
   and its value are separated by a "=" (equal sign). If present, these
   fields serve to identify the target of the URL.  For example, the
   OBJECT-VERSION field can be specified to identify a specific version
   of an object.

4. REGISTRATION OF NEW SCHEMES

   A new scheme may be introduced by defining a mapping onto a
   conforming URL syntax, using a new prefix. URLs for experimental
   schemes may be used by mutual agreement between parties. Scheme names
   starting with the characters "x-" are reserved for experimental
   purposes.

   The Internet Assigned Numbers Authority (IANA) will maintain a
   registry of URL schemes. Any submission of a new URL scheme must
   include a definition of an algorithm for accessing of resources
   within that scheme and the syntax for representing such a scheme.

   URL schemes must have demonstrable utility and operability.  One way
   to provide such a demonstration is via a gateway which provides
   objects in the new scheme for clients using an existing protocol.  If



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   the new scheme does not locate resources that are data objects, the
   properties of names in the new space must be clearly defined.

   New schemes should try to follow the same syntactic conventions of
   existing schemes, where appropriate.  It is likewise recommended
   that, where a protocol allows for retrieval by URL, that the client
   software have provision for being configured to use specific gateway
   locators for indirect access through new naming schemes.

   The following scheme have been proposed at various times, but this
   document does not define their syntax or use at this time. It is
   suggested that IANA reserve their scheme names for future definition:

   afs              Andrew File System global file names.
   mid              Message identifiers for electronic mail.
   cid              Content identifiers for MIME body parts.
   nfs              Network File System (NFS) file names.
   tn3270           Interactive 3270 emulation sessions.
   mailserver       Access to data available from mail servers.
   z39.50           Access to ANSI Z39.50 services.

5. BNF for specific URL schemes

   This is a BNF-like description of the Uniform Resource Locator
   syntax, using the conventions of RFC822, except that "|" is used to
   designate alternatives, and brackets [] are used around optional or
   repeated elements. Briefly, literals are quoted with "", optional
   elements are enclosed in [brackets], and elements may be preceded
   with <n>* to designate n or more repetitions of the following
   element; n defaults to 0.

; The generic form of a URL is:

genericurl     = scheme ":" schemepart

; Specific predefined schemes are defined here; new schemes
; may be registered with IANA

url            = httpurl | ftpurl | newsurl |
                 nntpurl | telneturl | gopherurl |
                 waisurl | mailtourl | fileurl |
                 prosperourl | otherurl

; new schemes follow the general syntax
otherurl       = genericurl

; the scheme is in lower case; interpreters should use case-ignore
scheme         = 1*[ lowalpha | digit | "+" | "-" | "." ]



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schemepart     = *xchar | ip-schemepart


; URL schemeparts for ip based protocols:

ip-schemepart  = "//" login [ "/" urlpath ]

login          = [ user [ ":" password ] "@" ] hostport
hostport       = host [ ":" port ]
host           = hostname | hostnumber
hostname       = *[ domainlabel "." ] toplabel
domainlabel    = alphadigit | alphadigit *[ alphadigit | "-" ] alphadigit
toplabel       = alpha | alpha *[ alphadigit | "-" ] alphadigit
alphadigit     = alpha | digit
hostnumber     = digits "." digits "." digits "." digits
port           = digits
user           = *[ uchar | ";" | "?" | "&" | "=" ]
password       = *[ uchar | ";" | "?" | "&" | "=" ]
urlpath        = *xchar    ; depends on protocol see section 3.1

; The predefined schemes:

; FTP (see also RFC959)

ftpurl         = "ftp://" login [ "/" fpath [ ";type=" ftptype ]]
fpath          = fsegment *[ "/" fsegment ]
fsegment       = *[ uchar | "?" | ":" | "@" | "&" | "=" ]
ftptype        = "A" | "I" | "D" | "a" | "i" | "d"

; FILE

fileurl        = "file://" [ host | "localhost" ] "/" fpath

; HTTP

httpurl        = "http://" hostport [ "/" hpath [ "?" search ]]
hpath          = hsegment *[ "/" hsegment ]
hsegment       = *[ uchar | ";" | ":" | "@" | "&" | "=" ]
search         = *[ uchar | ";" | ":" | "@" | "&" | "=" ]

; GOPHER (see also RFC1436)

gopherurl      = "gopher://" hostport [ / [ gtype [ selector
                 [ "%09" search [ "%09" gopher+_string ] ] ] ] ]
gtype          = xchar
selector       = *xchar
gopher+_string = *xchar




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; MAILTO (see also RFC822)

mailtourl      = "mailto:" encoded822addr
encoded822addr = 1*xchar               ; further defined in RFC822

; NEWS (see also RFC1036)

newsurl        = "news:" grouppart
grouppart      = "*" | group | article
group          = alpha *[ alpha | digit | "-" | "." | "+" | "_" ]
article        = 1*[ uchar | ";" | "/" | "?" | ":" | "&" | "=" ] "@" host

; NNTP (see also RFC977)

nntpurl        = "nntp://" hostport "/" group [ "/" digits ]

; TELNET

telneturl      = "telnet://" login [ "/" ]

; WAIS (see also RFC1625)

waisurl        = waisdatabase | waisindex | waisdoc
waisdatabase   = "wais://" hostport "/" database
waisindex      = "wais://" hostport "/" database "?" search
waisdoc        = "wais://" hostport "/" database "/" wtype "/" wpath
database       = *uchar
wtype          = *uchar
wpath          = *uchar

; PROSPERO

prosperourl    = "prospero://" hostport "/" ppath *[ fieldspec ]
ppath          = psegment *[ "/" psegment ]
psegment       = *[ uchar | "?" | ":" | "@" | "&" | "=" ]
fieldspec      = ";" fieldname "=" fieldvalue
fieldname      = *[ uchar | "?" | ":" | "@" | "&" ]
fieldvalue     = *[ uchar | "?" | ":" | "@" | "&" ]