Network Working Group                                      D. Zigmond
  Internet-Draft                                    Wink Communications
  draft-zigmond-media-url-00.txt                           October 1996
  Expire in six months
  
  
       Uniform Resource Locators for Television and Telephony
  
  
  . Status of this Document
  
  This document is an Internet-Draft.  Internet-Drafts are working
  documents of the Internet Engineering Task Force (IETF), its Areas,
  and its Working Groups.  Note that other groups may also distribute
  working documents as Internet-Drafts.
  
  Internet-Drafts are working documents valid for a maximum of six
  months.  Internet-Drafts may be updated, replaced, or obsoleted by
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  To learn the current status of any Internet-Draft, please check the
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  munnari.oz.au.
  
  Distribution of this document is unlimited.  Please send comments to
  dan.zigmond@wink.com.
  
  
  . Introduction
  
  World-Wide Web browsers are starting to appear on a variety of
  consumer electronic devices, such as televisions and both cellular and
  wireline telephones.  On these devices, some of the URL schemes
  described in [1] are inappropriate.  For example, many of these
  devices lack local storage, so the "file" scheme is of little use.
  However, these devices usually have access to other sources of
  information, such as television broadcasts and voice telephone
  services.  This draft proposes three new URL schemes for accessing
  such information on appropriate devices.
  
  
  . Television Tuning URL
  
  The basic structure of a television URL is:
  
       tv://<channel>
  
  where channel is an alpha-numeric description of the channel or
  network to be tuned.  This can be either a channel number, or a
  standard broadcaster identifier.  For example:
  
       tv://nbc            tune to the NBC network
       tv://wqed           tune to the WQED station
       tv://12                  tune to channel 12
  
  Note that for a browser to understand non-numeric channel identifiers,
  it will require a local channel map for the device.  The nature of
  this map and the way in which it is used will be browser- and
  device-specific and is beyond the scope of this draft.  In this way,
  the "tv" scheme is somewhat analagous to the "news" and "file" schemes
  in [1], in that it merely names a television broadcast signal but
  assumes that the local browser has some means for actually retrieving
  that signal on the local device.
  
  
  . Telephone Dialing URL
  
  The basic structure of a telephone URL is:
  
       phone://[+<country-code>-]<phone-number>
  
  where where both country-code and telephone-number are numeric
  strings.  The phone-number may contain one or more hyphens ("-"); the
  country-code cannot.  The effect of "fetching" a telephone URL is for
  the device to dial the given phone number.  For example:
  
       phone://+1-510-337-6359       dial a number in North America
       phone://800-943-9465          dial a number in the local country
  
  The first form (with country-code) is strongly recommended since it is
  the only form that can be unambiguously parsed internationally.  The
  device processing the phone URL is responsible for converting the URL
  into the actual string of digits that needs to be dialed, potentially
  adding digits particular to the local phone system or removing digits
  not required to place the call from a given location.  The way in
  which this is done will be browser- and device-specific and is beyond
  the scope of this draft.
  
  Unlike the "tv" scheme above (but like "fax" below), "phone" does
  not designate a data object to be directly accessed.  In this way, it
  is analogous to the "mailto" scheme in [1].
  
  
  . Facsimile Transmission URL
  
  A fax URL describes a phone number to which facsimile transmissions
  can be sent.  It has a form very similar to the "phone" scheme above:
  
       fax://[+<country-code>-]<phone-number>
  
  where the country-code and phone-number follow the same rules as for
  "phone" URLs.  For example:
  
       fax://+1-510-337-2960         send a fax in North America
  
  Like "phone" above, the "fax" scheme is closely related to the
  "mailto" scheme in [1], in that it it does not represent a data
  object to be accessed directly.
  
  
  . BNF for Television and Telephone URLs
  
  The following is a formal specification for the new URLs:
  
  tvurl          = "tv://" channel
  phoneurl       = "phone://" ["+" country-code "-"] phone-number
  faxurl         = "fax://" ["+" country-code "-"] phone-number
  
  channel        = *[ alpha | digit ]
  country-code   = * digit
  phone-number   = digit *[ digit | "-" ]
  
  
  The following definitions are from RFC 1738. Between the Internet Draft
  version and RFC 1738 two relevant changes were made: '=' was moved from
  the <extra> character class to <reserved>, and <national> was removed from
  the alternatives in <unreserved>. Neither <national> nor <punctuation> is
  referred to in this document nor in RFC 1738.
  
  lowalpha       = "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"
  hialpha        = "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"
  
  alpha          = lowalpha | hialpha
  digit          = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" |
                   "8" | "9"
  safe           = "$" | "-" | "_" | "." | "+"
  extra          = "!" | "*" | "'" | "(" | ")" | ","
  national       = "{" | "}" | "|" | "\" | "^^" | "~" | "[" | "]" | "`"
  punctuation    = "<" | ">" | "#" | "%" | <">
  
  reserved       = ";" | "/" | "?" | ":" | "@" | "&" | "="
  hex            = digit | "A" | "B" | "C" | "D" | "E" | "F" |
                   "a" | "b" | "c" | "d" | "e" | "f"
  escape         = "%" hex hex
  unreserved     = alpha | digit | safe | extra
  uchar          = unreserved | escape
  xchar          = unreserved | reserved | escape
  digits         = 1*digit
  
  
  . Acknowledgments
  
  Many of the ideas in this document came out of conversations with
  Andrew Lochart.  Other people who supplied valuable input include Matt
  Trifiro and Eric Del Sesto.
  
  
  . Security Considerations
  
  The two new URL schemes are subject to the same security implications
  as the general URL scheme [1], so the usual precautions apply.  This
  means, for example, that a locator might no longer point to the object
  that was originally intended.  It also means that it may be possible
  to construct a URL so that an attempt to perform a harmless idempotent
  operation such as the retrieval of an object will in fact cause a
  possibly damaging remote operation to occur.  The telephone dialing
  URL, in particular, may cause an unwanted telephone call to be placed,
  possibly resulted in additional telephone charges to the user.
  
  
  . References
  
     [] Berners-Lee, T., Masinter, L., McCahill, M. (editors), "Uniform
         Resource Locators (URL)", RFC 1738, December 1994.
         ftp://ds.internic.net/rfc/rfc1738.txt
  
  
  . Author's Address
  
  Dan Zigmond
  Wink Communications
   Marina Village Parkway
  Alameda CA 94501
  
  Email: dan.zigmond@wink.com
  Voice: +1-510-337-6359
  Fax:   +1-510-337-2960