The TV-Anytime Content Reference Identifier (CRID)
draft-earnshaw-tv-anytime-crid-04

Network Working Group                                        N. Earnshaw
Internet-Draft                              BBC Research and Development
Expires: May 23, 2005                                            S. Aoki
                                                    TokyoFM Broadcasting
                                                               A. Ashley
                                                             NDS Limited
                                                             W. Kameyama
                                                 GITS, Waseda University
                                                       November 22, 2004

           The TV-Anytime Content Reference Identifier (CRID)
                 draft-earnshaw-tv-anytime-crid-04.txt

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Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

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   The Uniform Resource Locator (URL) scheme "CRID:" has been devised to
   allow references to current or future scheduled publications of
   broadcast media content over television distribution platforms and
   the Internet.

   The initial intended application is as an embedded link within
   scheduled programme description metadata that can be used by the home
   user or agent to associate a programme selection with the
   corresponding programme location information for subsequent automatic
   acquisition.

   This document reproduces the TV-Anytime CRID definition found in the
   TV-Anytime content referencing specification, and is published as an
   RFC for ease of access and registration with the Internet Assigned
   Numbers Authority (IANA).

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Ancestry . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Notation used in this document . . . . . . . . . . . . . . . .  5
   4.  The CRID URL Scheme  . . . . . . . . . . . . . . . . . . . . .  5
   5.  Examples of CRID syntax  . . . . . . . . . . . . . . . . . . .  5
   6.  Usage  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     6.1   Normative Specification  . . . . . . . . . . . . . . . . .  6
     6.2   Role of Domain Name System (DNS) namespace . . . . . . . .  6
     6.3   CRID resolving . . . . . . . . . . . . . . . . . . . . . .  6
     6.4   CRID Related Metadata  . . . . . . . . . . . . . . . . . .  7
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
     7.1   General  . . . . . . . . . . . . . . . . . . . . . . . . .  7
     7.2   Registration Template in accordance with RFC2717 . . . . .  7
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 10
   A.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
       Intellectual Property and Copyright Statements . . . . . . . . 12

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1.  Introduction

   In recent years there has been an expansion in the number of
   broadcast television and radio services available to the home.  In
   addition to the broadcast services delivered over traditional
   distribution channels such as Digital Terrestrial, Satellite and
   Cable, the advent of high speed internet connection to the home will
   give rise to new information and entertainment services providing
   audio visual programme material sourced directly to the home over the
   Internet.

   Alongside this expansion there is also an increased growth in
   complexity of the device available to the home user that will allow
   the home user to operate in a 'search-select-acquire' paradigm.  In
   this model the user or user agent uses descriptive information about
   audio visual programmes as a basis for selecting the programme for
   subsequent acquisition and viewing.  Increasingly home appliances are
   being furnished with local storage enabling the automatic capture of
   the programme material through off air recording or downloading by
   the home appliance.

   The 'CRID:' Uniform Resource Locator is designed to be the bridge
   between programme related descriptive metadata and corresponding
   programme location data that may be published over a different
   distribution network or at a different time.

   Programme location data provides the home user agent with the
   information required to acquire the programme at the time of
   publication.  In the case of the television distribution model these
   locators provide programme broadcast timing and tuning information
   such that the user appliance can record the programme when broadcast
   in real time.  For the case of internet delivery the locators need to
   be of the form associated with streaming protocols or file exchange
   protocols with the time (or time window) of availability indicated.

   Since a content publisher may release audio video material in the
   same form on a number of platforms, or repeatedly over some time
   interval, the CRID can be used to aggregate these different
   publications and associate them with a single description.
   Furthermore, there may be other meaningful semantic associations
   between otherwise unrelated programme publications with assigned CRID
   that can be further aggregated under a higher level CRID.  This
   higher level CRID can be described through its own descriptive
   metadata.  The subjective nature of such aggregation decisions is
   part of the CRID authoring process and is not standardised.

   The CRID resolution process ultimately enabling the user agent to
   acquire the audio visual programme material may be a timely process,

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   with resolution updates delivered dynamically from the service
   provider.  This is to reflect common business practice of adjusting
   the time of content availability close to the original published time
   to accommodate a live, managed, reactive broadcast service.

2.  Ancestry

   The Uniform Resource Locator scheme 'CRID:' is taken from the
   TV-Anytime forum Content Reference Identifier and is a result of the
   consensus reached by members of this forum between March 2000 and
   June 2002.  The TV-Anytime CRID and associated supporting data is
   specified in the TV-Anytime Phase 1 Content Referencing Specification
   [TVA-CR].

3.  Notation used in this document

   The notation used in this document takes the form

               <first>/<second>

   in which the component names are in angle brackets and any characters
   outside angle brackets are literal separators.

4.  The CRID URL Scheme

   The CRID URL takes the form

               crid://<DNS name>/<data>

   where <DNS name> is a registered internet domain name which takes the
   form of domain name described in Section 3 of [RFC1034] and Section
   2.1 of [RFC1123].

   <data> is a free format string that is URI [RFC2396] compliant, and
   is meaningful to the authority given by the authority field.  The
   portion of the field is case insensitive.  It is recommended that all
   characters not within the range of characters allowed in a URI must
   be encoded into UTF-8 and included in the URI as a sequence of
   escaped octets.  An escaped octet is encoded as a character triplet,
   consisting of the percent character "%" followed by the two
   hexadecimal digits representing the octet code.

   In its entirety, the CRID is URI compliant as specified in [RFC2396].
   As per [RFC2396] the crid:// part of the syntax is case insensitive.

5.  Examples of CRID syntax

   Examples of valid CRID.

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            crid://example.com/foobar

   CRID created by "example.com" authority, with data part of foobar.

            crid://example.co.jp/%E3%82%A8%E3%82%A4%E3%82%AC

   CRID created by "example.co.jp" authority, with a data part of "E",
   "I" and "GA" (meaning "movie"), represented as KATAKANA LETTERS
   (Japanese characters) in UTF-8 encoding preceded by "%".

6.  Usage

6.1  Normative Specification

   The Uniform Resource Locator scheme 'CRID:' identifies the URL as the
   TV-Anytime Content Reference Identifier and conforms to the
   TV-Anytime Content Referencing Specification [TVA-CR].  The
   TV-Anytime CRID is a key component in the TV-Anytime forum
   specification series as described in the informative overview Systems
   Description Specification [TVA-Sys].  The normative Content
   Referencing Specification [TVA-CR] also includes the details of the
   contents and format of the associated content referencing tables that
   resolve the TV-Anytime CRID into further CRID instances or transport
   system dependent locations.

6.2  Role of Domain Name System (DNS) namespace

   It is important to note that the use of the registered Internet
   Domain does not mean the DNS resolving service is to be employed for
   the resolution of CRID URL.  Indeed the resolution information is
   fully specified in [TVA-CR] and does not require the use of the DNS
   resolution service.  This is especially important as one key
   application area is broadcast television and radio distribution
   services that are not internet based.

   For the case of business scenarios that do exploit Internet
   connectivity to the home, the DNS portion of the CRID can be used to
   resolve the internet location of the service provider who in turn
   will provide location resolution information in a form described in
   [TVA-CR].

6.3  CRID resolving

   As addressed in [TVA-CR] the CRID is ultimately resolved either
   directly by the CRID authority or by another party.  If another party
   is providing resolution, the ability to resolve the CRID requires the
   flow of some information from the authority to the resolution
   provider, in order to tie the CRID to its resolution.  Examples of

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   relationships between CRID authors and the suppliers of resolution
   information are given in [TVA-Sys].

   As described in [TVA-CR] there will in all likelihood be more than
   one CRID that can resolve directly or indirectly to a given single
   locator at a given time.

   Also shown in [TVA-CR] CRIDs that resolve directly to the location of
   the scheduled content are likely to resolve to more than one location
   as television and radio programmes are often published repeatedly
   within broadcast schedules or across different broadcast services or
   distribution platforms over an extended period of time.

6.4  CRID Related Metadata

   TV-Anytime specification [TVA-Met] specifies the format and contents
   of the programme related descriptive metadata designed to convey the
   TV-Anytime CRID for the purpose outlined here as well as other data
   supporting the publication and usage of programme material.

7.  IANA Considerations

7.1  General

   The 'crid:' URI scheme should be reserved to designate that the URI
   relates to the TV-Anytime CRID and is to be used in accordance with
   the TV-Anytime Content Referencing Specification [TVA-CR].

   The designation of the value of each CRID is the responsibility of
   the CRID author, as identified through the 'authority' field.

   The policy of assignment of CRID values lies with the CRID author
   associated with the authority field.  It is likely that there will be
   a number of diverse (and possibly changing) authoring policies as
   required by various organisations as they address their respective
   audiences.  These individual policies will address such resolution
   target resource designation issues as: the subjective equivalence of
   programme material available from different locations, the grouping
   of CRIDs under another CRID for collective description and resolution
   purposes, the cross referencing of CRID between authorities, CRID
   lifetime and CRID reuse.

   It is likely that some authoring policies may be set through
   collaborative business arrangements, localised operational agreements
   or through national governmental bodies.

7.2  Registration Template in accordance with RFC2717

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   URL scheme name: crid

   URL scheme syntax: See Section 4

   Character encoding considerations: TV-Anytime does not specify the
   character encoding scheme to be adopted by each implementation.
   However, in the case where internet interoperability is desired, it
   is recommended that all characters not within the range of characters
   allowed in a URI must be encoded into UTF-8 and included in the URI
   as a sequence of escaped octets.  An escaped octet is encoded as a
   character triplet, consisting of the percent character "%" followed
   by the two hexadecimal digits representing the octet code.  For
   example, the character A would be represented as "A", the character
   LATIN CAPITAL LETTER A WITH GRAVE would be represented as "%C3%80",
   and the character KATAKANA LETTER A would be represented as
   "%E3%82%A2".

   Intended Use: See Section 6

   Application and protocols which use this scheme: See Section 6

   Interoperability considerations: None (Section 4 contains the first
   version of the CRID URL definition)

   Security considerations: See Section 8

   Relevant publications: See [TVA-CR], [TVA-Met], [TVA-Sys], [TVA-Prt]

   Contact: Wataru KAMEYAMA, Vice Chairman and Secretary of the
   TV-Anytime Forum, wataru@waseda.jp

   Author/Change controller: IESG

8.  Security Considerations

   The CRID URL described here provides a referencing mechanism.  The
   values of the URL contain the authoring 'Authority' name as a DNS
   namespace identifier and a data portion to distinguish it from other
   CRIDs from the same authority.  There should be no reason to prevent

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   disclosure of the values within the CRID and no commercial
   sensitivity associated with these values.

   When conveyed as part of a larger data set which may have commercial
   value or critical binding between a CRID and the accompanying data,
   then the security and integrity of the binding is a matter for the
   wider system implementers to judge and protect accordingly.  One such
   method for protecting metadata can be found in [TVA-Prt], though it
   is not mandated that users adopt this.  In any case there may be
   other wider system security functions in place or the absence of
   perceived need for such precautions.

   Tampering with values of CRIDs during transmission or distribution
   over public or open networks has only nuisance or denial of service
   effects unless it causes alternative location resolution data or
   programme metadata to be referenced.  Again this can be dealt with as
   a system delivery of data integrity issue not specific to the CRID.

   Impersonating a CRID authority by authoring CRID with an authority
   portion for which the bogus author does not have permission from the
   registered DNS name holder would be a misuse of the DNS name holder's
   identity and should be dealt with through normal business practice.

9  References

   [TVA-Sys]  European Telecommunications Standards Institute, "ETSI TS
              102 822-2 v1.2.1 ; Broadcast and On-line Services: Search,
              select and rightful use of content on personal storage
              systems ("TV-Anytime Phase 1"). Part 2 System
              Description", September 2004.

   [TVA-CR]   European Telecommunications Standards Institute, "ETSI TS
              102 822-4 v1.1.2 ; Broadcast and On-line Services: Search,
              select and rightful use of content on personal  storage
              systems ("TV-Anytime Phase 1"); Part 4: Content
              referencing", October 2004.

   [TVA-Met]  European Telecommunications Standards Institute, "ETSI TS
              102 822-3-1 v1.2.1 ; Broadcast and On-line Services:
              Search, select and rightful use of content on personal
              storage systems ("TV-Anytime Phase 1"). Part 3 Metadata.
              Sub-part 1: Metadata Schemas", September 2004.

   [TVA-Prt]  European Telecommunications Standards Institute, "ETSI TS
              102 822-7 v1.1.1 ; Broadcast and On-line Services: Search,
              select and rightful use of content on personal  storage
              systems ("TV-Anytime Phase 1"). Part 7 Bi-directional
              Metadata Delivery Protection", October 2003.

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   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              November 1987.

   [RFC1123]  Braden, R., "Requirements for Internet Hosts - Application
              and Support", October 1989.

   [RFC2396]  Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
              Resource Identifiers (URI): Generic Syntax", August 1998.

   [RFC2717]  Petke, R. and I. King, "Registration Procedures for URL
              Scheme Names", November 1999.

Authors' Addresses

   Nigel Earnshaw
   BBC Research and Development
   Kingswood Warren
   Tadworth, Surrey  KT20 6NP
   United Kingdom

   Phone: +44 1737 839618
   EMail: nigel.earnshaw@rd.bbc.co.uk

   Shigeru Aoki
   TokyoFM Broadcasting
   1-7 Kojimachi
   Chiyoda-ku, TOKYO  102-8080
   JAPAN

   Phone: +81 3 3221 0244
   EMail: shig@center.jfn.co.jp

   Alex Ashley
   NDS Limited
   One London Road
   Staines, Middlesex  TW18 4EX
   United Kingdom

   Phone: +44 208 4768270
   EMail: aashley@ndsuk.com

   Wataru Kameyama
   GITS, Waseda University
   1011 Okuboyama, Nishi-tomida

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   Honjo-shi, SAITAMA  367-0035
   JAPAN

   Phone: +81 495 24 6052
   EMail: wataru@waseda.jp

Appendix A.  Acknowledgements

   The authors would like to acknowledge the support of the members of
   the TV-Anytime forum and their work in the development of the
   TV-Anytime CRID.

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