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Digital Video Broadcasting (DVB); Uniform Resource Identifiers (URI) for DVB Systems DVB Document A142 December 2010 3 Contents Intellectual Property Rights ................................................................................................................................ 4   Foreword............................................................................................................................................................. 4   Introduction ........................................................................................................................................................ 5   1 Scope ........................................................................................................................................................ 6   2 References ................................................................................................................................................ 6   3 Definitions, symbols and abbreviations ................................................................................................... 7   3.1 Definitions ......................................................................................................................................................... 7   3.2 Abbreviations ..................................................................................................................................................... 7   4 URL Schemes for Access to DVB Services ............................................................................................. 8   5 Encoding of URI strings and the use of non-Latin characters.................................................................. 8   6 ......................................................................................................................... 9   6.1 .................................................................................................................... 9   6.2 URLs including path references....................................................................................................................... 12   6.2.1 dvb_entity = dvb_service ........................................................................................................................... 12   6.2.2 dvb_entity = dvb_service_component ........................................................................................................ 12   6.2.3 dvb_hier_part = dvb_abs_path ................................................................................................................... 12   6.2.4 dvb_abs_path.............................................................................................................................................. 12   6.2.5 dvb_entity = dvb_transport_stream ............................................................................................................ 13   6.2.6 Reserved Names ......................................................................................................................................... 13   6.3 Interactive application specific locators ........................................................................................................... 13   6.3.1 Extended Application Locator.................................................................................................................... 13   6.3.2 TV Locators ............................................................................................................................................... 14   6.3.3 Application Locator.................................................................................................................................... 14   6.3.4 AIT Locators .............................................................................................................................................. 15   6.3.5 Exit Locator ................................................................................................................................................ 15   6.3.6 Server Domain ........................................................................................................................................... 15   6.4 EPG, BCG and ESG Specific Locators ........................................................................................................... 16   6.4.1 DVB Event Constraint ............................................................................................................................... 16   6.4.2 Restrictions of EPG, BCG and ESG Specific Locators .............................................................................. 16   6.4.3 Locators in Metadata .................................................................................................................................. 17   6.5 Resolution ........................................................................................................................................................ 17   8 ........................................................................................................................... 18   8.1 ................................................................................................... 18   8.2 ..................................................................................................... 18   A nnex A (informative): Bibliography ........................................................................................................... 19   History .............................................................................................................................................................. 21     DVB BlueBook A142 4 Intellectual Property Rights IPRs  essential  or  potentially  essential  to  the  present  document  may  have  been  declared  to  ETSI.  The   information  pertaining  to  these  essential  IPRs,  if  any,  is  publicly  available  for  ETSI  members  and  non-­ members,  and  can  be  found  in  ETSI  SR  000  314:  "Intellectual  Property  Rights  (IPRs);  Essential,  or   potentially  Essential,  IPRs  notified  to  ETSI  in  respect  of  ETSI  standards",  which  is  available  from  the  ETSI   Secretariat.  Latest  updates  are  available  on  the  ETSI  Web  server   (http://webapp.etsi.org/IPR/home.asp).   Pursuant  to  the  ETSI  IPR  Policy,  no  investigation,  including  IPR  searches,  has  been  carried  out  by  ETSI.   No  guarantee  can  be  given  as  to  the  existence  of  other  IPRs  not  referenced  in  ETSI  SR  000  314  (or  the   updates  on  the  ETSI  Web  server)  which  are,  or  may  be,  or  may  become,  essential  to  the  present   document.   Foreword This  Technical  Specification  (TS)  has  been  produced  by  Joint  Technical  Committee  (JTC)  Broadcast  of   the  European  Broadcasting  Union  (EBU),  ComitéEuropéen  de  Normalisation  ELECtrotechnique   (CENELEC)  and  the  European  Telecommunications  Standards  Institute  (ETSI).   NOTE:   The  EBU/ETSI  JTC  Broadcast  was  established  in  1990  to  co-­‐ordinate  the  drafting  of   standards  in  the  specific  field  of  broadcasting  and  related  fields.  Since  1995  the  JTC   Broadcast  became  a  tripartite  body  by  including  in  the  Memorandum  of  Understanding   also  CENELEC,  which  is  responsible  for  the  standardization  of  radio  and  television   receivers.  The  EBU  is  a  professional  association  of  broadcasting  organizations  whose  work   includes  the  co-­‐ordination  of  its  members'  activities  in  the  technical,  legal,  programme-­‐ making  and  programme-­‐exchange  domains.  The  EBU  has  active  members  in  about  60   countries  in  the  European  broadcasting  area;  its  headquarters  is  in  Geneva.     European  Broadcasting  Union   CH-­‐1218  GRAND  SACONNEX  (Geneva)   Switzerland   Tel:   +41  22  717  21  11   Fax:   +41  22  717  24  81   Founded  in  September  1993,  the  DVB  Project  is  a  market-­‐led  consortium  of  public  and  private  sector   organizations  in  the  television  industry.  Its  aim  is  to  establish  the  framework  for  the  introduction  of   MPEG-­‐2  based  digital  television  services.  Now  comprising  over  200  organizations  from  more  than  25   countries  around  the  world,  DVB  fosters  market-­‐led  systems,  which  meet  the  real  needs,  and  economic   circumstances,  of  the  consumer  electronics  and  the  broadcast  industry.       DVB BlueBook A142 5 Proposed  national  transposition  dates   Date  of  latest  announcement  of  this  EN  (doa):   3  months  after  ETSI  publication   Date  of  latest  publication  of  new  National  Standard     or  endorsement  of  this  EN  (dop/e):   6  months  after  doa   Date  of  withdrawal  of  any  conflicting  National  Standard  (dow):   6  months  after  doa     Introduction In  its  current  strict  technical  meaning,  a  URL  (Uniform  Resource  Locator)  is  a  URI  (Uniform  Resource   describing  its  primary  access  mechanism  (e.g.  its     was  used  widely  for  designating  network-­‐retrievable  documents  which  were  the  core  idea  of  the   World  Wide  Web.  This  unprecise  use  of  the  term  has  continued  until  to  date.   -­‐ independent  resource  identifiers  and  are  designed  to  make  it  easy  to  map  other  namespaces  (that   share  the  properties  of  URNs)  into  URN-­‐space.  Therefore,  the  URN  syntax  provides  a  means  to  encode   character  data  in  a  form  that  can  be  sent  in  existing  protocols,  tra [RFC  2141].   So  a  URN  globally  refers  to  an  entity  regardless  from  where  and  how  it  may  be  retrieved,  whilst  a  URL   globally  refers  to  a  location  without  implying  anything  about  the  object  that  can  be  retrieved  from  that   location.  Both,  URNs  and  URLs  are  subsets  of  URI.       DVB BlueBook A142 6 1 Scope The  present  document  specifies  the  syntax,  semantics  and  encoding  of  the  Uniform  Resource  Identifier   (URI)  schemes  for  use  with  DVB  systems.  The  following  URI  schemes  are  covered:   dvb:   exit:   These  URI  schemes  shall  be  used  to  refer  to  locations  on  DVB  networks  from  both,  within  DVB   networks  and  from  outside  of  DVB  networks.     2 References The  following  documents  contain  provisions  which,  through  reference  in  this  text,  constitute   provisions  of  the  present  document.   References  are  either  specific  (identified  by  date  of  publication  and/or  edition  number  or   version  number)  or  non-­‐specific.   For  a  specific  reference,  subsequent  revisions  do  not  apply.   For  a  non-­‐specific  reference,  the  latest  version  applies.   Referenced  documents  which  are  not  found  to  be  publicly  available  in  the  expected  location  might  be   found  at  http://docbox.etsi.org/Reference.    [ISO  13818]   ISO/IEC  13818-­‐ -­‐  Generic  coding  of  moving  pictures  and     ISO-­‐IEC  13818-­‐ -­‐  Generic  coding  of  moving  pictures  and     ISO-­‐IEC  13818-­‐ -­‐  Generic  coding  of  moving  pictures  and     ISO-­‐IEC  13818-­‐ -­‐  Generic  coding  of  moving  pictures  and     ISO-­‐IEC  13818-­‐ -­‐  Generic  coding  of  moving  pictures  and   associated  audio  information:  Extensions  for  DSM-­‐   ISO-­‐IEC  13818-­‐ -­‐  Generic  coding  of  moving  pictures  and   associated  audio  information:  Extension  for  real  time  interface  for  systems     ISO-­‐IEC  13818-­‐  technology  -­‐  Generic  coding  of  moving  pictures  and   associated  audio  information:  Conformance  extensions  for  Digital  Storage  Media   Command  and  Control  (DSM-­‐   [EN  300  468]     DVB BlueBook A142 7 [TS  102  812]   ETSI  TS  102  812   [TS  102  323]   -­‐   [ISO  8601]   ISO/IEC  8601  (2002):   -­‐  Information   interchange  -­‐     [EG  201  212]   ETSI  EG  201  212:  "Electrical  safety;  Classification  of  interfaces  for  equipment  to  be   connected  to  telecommunication  networks".   [EN  300  429]   ETSI  EN  300  429:  "Digital  Video  Broadcasting  (DVB);  Framing  structure,  channel   coding  and  modulation  for  cable  systems".   [RFC  5328]   Video     A.  Adolf  /  P.  MacAvock   September  2008   [TR  102  679]   ETSI  TR  102  679   [EN  301  192]   pecification  for  data     [RFC  2234]     D.  Crocker  (Editor)  /  P.  Overell   November  1997   3 Definitions, symbols and abbreviations 3.1 Definitions For  the  purposes  of  the  present  document,  the  terms  and  definitions  given  in  [EN  300  468]  apply.   3.2 Abbreviations For  the  purposes  of  the  present  document,  the  following  abbreviations  apply:   AIT   Application  Information  Table  [TS  102  812]   ABNF   Augmented  Backus-­‐Naur  Form  [RFC  2234].   BCG   Broadband  Content  Guide   EPG   Electronic  Programme  Guide  [EN  300  468]   ESG   Electronic  Service  Guide   DAVIC   Digital  Audio  Video  Council  (www.davic.org)   DVB BlueBook A142 8 DVB   Digital  Video  Broadcasting  (www.dvb.org)   ECG   Electronic  Content  Guide   ESG   Electronic  Service  Guide   IETF   Internet  Engineering  Task-­‐Force  (www.ietf.org)   IP   Internet  Protocol  [RFC  791]   NIT   Network  Information  Table  [EN  300  468]   NSAP   Network  Service  Access  Point   RFC   Request  for  Comments  (published  by  IETF,  see  www.faqs.org)   SD&S   Service  Discovery  and  Selection   URL   Uniform  Resource  Locator     4 URL Schemes for Access to DVB Services DVB  has    as  of  this  writing    defined  two  environments  for  broadcast,  interactive  and  on-­‐demand   services:     based  on  MPEG-­‐2  Transport  Stream  [ISO  13818].     the  IP  protocol  [RFC  791].   DVB  defines  the  following  general  format  of  the  URLs:   :////...//   The  protocol    part  of  the  URL  identifies  that  it  is  a  DVB  service.  All  DVB  defined  protocol  tags  begin     The  server  part  of  the  URL  points  to  the  network  service  access  point  (NSAP)  as  services  are  the  basic   element  that  is  carried  in  DVB  networks.  The  rest  of  the  URL  specifies  the  individual  component   relative  to  the  respective  NSAP.   The  format  of  the  object  part  is  dependent  on  the  type  of  the  service.  This  part  is  not  needed  if  the  URL   points  to  the  whole  service.   5 Encoding of URI strings and the use of non-Latin characters The  URI  format  (see  [RFC  3986])  consists  of  a  sequence  of  a  limited  range  of  Latin  characters  plus  a   DVB BlueBook A142 9 for  non-­‐Latin  characters  to  be  used  in  URIs,  a  standard  mapping  from  those  non-­‐Latin  characters  is   defined.   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.     6 DVB  defines  a  specific  Uniform  Resource  Locator  (URL)  format  which  provides  a  general  addressing   mechanism  intended  to  access  broadcast  services  from  interactive  applications  or  services.   DVB  URLs  may  be  used  from  an  interactive  application  to  address  any  of  the  following;   A  DVB  service   One  or  more  components  of  a  DVB  service  -­‐  for  example  video,  audio  or  subtitle  elementary   streams   An  event  in  a  DVB  service   A  transport  stream  in  a  DVB  network   A  file  carried  in  a  DSM-­‐CC  object  carousel   Another  interactive  application   Which  of  these  can  be  used  and  how  they  are  used  should  be  defined  in  the  specification  for  the   technology  in  which  the  interactive  application  is  written  or  distributed.   DVB  broadcast  networks  carry  Service  Information  (SI)  which  contains  globally  unique  parameters  for   locating  services  in  the  broadcast  networks.  The  URL  format,  defined  by  DVB  to  access  such  services  is   based  on  these  parameters  as  they  provide  an  addressing  mechanism  in  a  physical  network   independent  way.  The  same  services  may  be  carried  simultaneously  in  many  physical  networks,  but   the  parameters  in  the  SI  will  remain  the  same  and  they  can  thus  be  used  by  the  clients  to  locate  the   services  regardless  of  the  actual  physical  network.   6.1 An  extended  format  of  the  DAVIC  DVB  URL  [DAVIC-­‐9]  shall  be  used  for  addressing  DVB-­‐SI  entities  as   well  as  files  within  object  carousels.  This  extension  of  the  DAVIC  locator  is  backwards  compatible  with   both  the  original  DAVIC  locator  as  well  as  the  UK  DTG  extension  [MHEG-­‐UK].  The  main  extensions  are   support  for  multiple  component  tags  for  specifying  a  subset  of  the  components  of  a  service,  and  a   specified  way  of  referencing  files  in  an  object  carousel  within  a  service.   The  following  locator  formats  shall  be  used:   DVB BlueBook A142 10 dvb://.[][.[.[$ ]][]][]   dvb://''[.[$]][][]   A  more  formal  specification  of  the  DVB  dvb:  URL  expressed  in  BNF  (as  used  in  [RFC  3986])  is   presented  in  table  1  below.   Table 1: Syntax of the dvb: URL dvb_url   =   dvb_scheme dvb_hier_part   dvb_scheme   =     dvb_hier_part   =   dvb_net_path  |  dvb_abs_path   dvb_abs_path   =   path-­‐absolute(see  note  2)   dvb_net_path   =   (  dvb_entity  [  dvb_abs_path  ]  )  |  dvbapp_entity(see  note  1)   dvb_entity   =   dvb_transport_stream  |  dvb_service  |  dvb_service_component   dvb_transport_stream   =   original_network_id transport_stream_id   dvb_service   =   dvb_service_without_event [ dvb_event_constraint(see note 3) ]   dvb_service_component   =   dvb_service_without_event component_set   [   dvb_carousel_id]   [  dvb_event_constraint(see  note  3)  ]   dvb_service_without_event   =   original_network_id [  transport_stream_id  ]   service_id   |   textual_service_identifier   dvb_carousel_id   =   transaction_id(see  note  5)   component_set   =   component_tag_set  |  qualified_component_set   |  fully_qualified_component_set   component_tag_set   =   component_tag  *(   component_tag  )   qualified_component_set   =   qualified_component  *(   qualified_component  )   qualified_component     component_type component_id   component_type   =   video  |   audio  |   data  |   subtitle  |   teletext  |   dvbst   component_id   =   component_string  |   default  |   current  |   hearing_impaired  |   |   none   component_string   =   iso639_language_code  |  component_tag   DVB BlueBook A142 11 fully_qualified_component_set   =   fully_qualified_component  *(   fully_qualified_component)   fully_qualified_component   =   stream_content_and_component_type component_tag   [  iso639_language_code  ]   stream_content_and_component_type   =   hex_string(see  note  6)   original_network_id   =   hex_string   transport_stream_id   =   hex_string   service_id   =   hex_string   component_tag   =   hex_string   event_id   =   hex_string   transaction_id   =   hex_string   textual_service_identifier   =   host(see  note  4)   iso639_language_code   =   3  (   -­  |   -­   hex_string   =   1  *  hex   hex   =   digit  |    |    |    |    |    |    |    |    |    |    |    |     digit   =    |    |    |    |    |    |    |    |    |     NOTE 1: See clause .3.1 Application format specific locator NOTE 2: path-absolute as defined in [RFC 3986] NOTE 3: .4 EPG, BCG and ESG Specific Locators NOTE 4: host as defined in [RFC 3986] NOTE 5: Data carousels NOTE 6: 12-bit hex string (3 hex chars) which is the stream_content followed by the component_type from the component descriptor [EN 300 468]   It  should  be  noted  that  this  syntax  is  fully  compliant  with  the  generic  syntax  of  URIs  as  specified  in   [RFC  3986]  and  uses  the  registry-­‐based  naming  authority  version  of  that.  Furthermore,  all  generic   definitions  specified  in  [RFC  3986]  shall  be  valid  for  the  DVB  URL  as  well  (e.g.  escaping  of  special   characters  within  file  names,  etc.).   [RFC  3986]  defines  methods  for  path  segments  to  include  parameters  (introduced  with  a  semicolon   character  ";").  This  specification  currently  makes  no  use  of  such  parameters.  Implementations   conforming  to  this  specification  shall  ignore  any  such  parameters  to  ensure  compatibility  with  future   specifications.   When  a  path  is  present  in  a  URL  where  the  dvb_entity  part  identifies  a  DVB  service,  the  path  references   an  object  in  an  object  carousel  within  the  service.  If  there  are  multiple  object  carousels  within  the   same  service,  the  rule  on  how  to  select  the    default    one  is  to  be  defined.   DVB BlueBook A142 12 6.2 URLs including path references When  a  path  is  present  in  a  URL  where  the  dvb_entity  part  identifies  one  component  of  a  DVB  service   and  that  component  carries  an  object  carousel  stream,  the  path  references  an  object  in  an  object   carousel  whose    root    (i.e.  DSI  message)  is  sent  within  that  component.  Note  that  the  referenced  object   itself  is  not  necessarily  carried  in  the  component  identified  in  the  URL,  but  the  component  in  the  URL   identifies  only  the  component  carrying  the  root  of  the  object  carousel  in  which  the  referenced  object  is   carried.   The  semantics  when  the  path  is  present  in  the  URL  and  where  the  dvb_entity  part  identifies  something   else  than  the  two  cases  described  above  is  not  defined  in  this  specification  and  is  reserved  for  future   use.   When  the  dvb_net_path  part  is  missing  and  only  the  dvb_abs_path  is  present,  the  URL  refers  to  a  file  in   a  default  object  carousel  within  the  current  service.  The    current    service  is  dependent  on  the  usage   context.   6.2.1 dvb_entity = dvb_service When  a  path  is  present  in  a  URL  where  the  dvb_entity  part  identifies  a  DVB  service,  the  path  references   an  object  in  an  object  carousel  within  the  service.  If  the  dvb_service_component  element  is  not  present   there  shall  only  be  one  Object  Carousel  in  the  DVB  service.   6.2.2 dvb_entity = dvb_service_component When  a  path  is  present  in  a  URL  where  the  dvb_entity  part  identifies  one  component  of  a  DVB  service   and  that  component  carries  an  object  carousel  stream,  the  path  references  an  object  in  an  object   carousel  whose  "root"  (i.e.  DSI  message)  is  sent  within  that  component.  In  this  case  the  component  tag   set  shall  only  contain  one  element.   The  semantics  when  the  path  is  present  in  URL  where  the  dvb_entity  part  identifies  something  else   than  the  two  cases  described  above  are  not  specified  in  this  specification.   6.2.3 dvb_hier_part = dvb_abs_path When  the  dvb_net_path  part  is  missing  and  only  the  dvb_abs_path  is  present,  the  URL  refers  to  a  file  in   a  default  object  carousel  within  the  current  service.  The  "current"  service  is  dependent  on  the  usage   context.   6.2.4 dvb_abs_path The  following  restrictions  apply  to  the  dvb_abs_path  part  of  a  name:   The  total  length  of  pathnames,  separators  and  file  name  shall  be  less  than  or  equal  to  254  bytes   long.   The  following  characters  are  not  allowed  in  file  names  and  pathnames:  character  null   (0xC080),  byte  zero.   The  encoding  of  the  file  name  is  in  UTF-­‐8.   DVB BlueBook A142 13 The  directory  separator  character  shall  be  a  slash  character  (0x2F).   An  absolute  file  name  starts  with  a  slash  character  (as  indicated  in  the  BNF  above).   6.2.5 dvb_entity = dvb_transport_stream At  least  the  numeric  identifiers  original_network_id,  transport_stream_id  and  service_id,  if  present,   shall  be  matched  against  the  corresponding    fields  in  DVB-­‐SI.   6.2.6 Reserved Names File  names  starting  with  the  characters  "dvb."  (dee-­‐vee-­‐bee-­‐ files  defined  in  this  or  future  specifications.   Authors  shall  not  use  file  names  with  this  form  to  avoid  possible  collision  with  standards  defined  files.   6.3 Interactive application specific locators Two  specific  formats  of  locators  are  defined  which  have  defined  semantics  only  in  the  context  of   specific  formats  for  interactive  applications:   The  extended  form  of  the  DVB  locator  (see  "6.3.1  Extended  Application  Locator")   The  exit  locator  used  for  application  self  termination  (see  "6.3.5  Exit  Locator")   6.3.1 Extended Application Locator The  formal  specifcation  of  the  URL  form  expressed  in  BNF  is  given  in  the  extension  in  table  2to  the   table  1in  clause     Table 2: Extended Application URL syntax dvbapp_entity(note  1)   =   dvb_service_contextual  |  dvb_service_component_contextual   |  ait_specifier   dvb_service_contextual   =    |     dvb_service_component_contextual   =         ait_specifier   =   ait_abs_path   ait_filter   =    |  dvb_service_without_event   ait_abs_path   =   ait_entity   ait_entity   =   ait_root_directory  |  ait_application   ait_root_directory   =     ait_application(note  2)   =   ait_params  ]   ait_params(note  3)   =    1*digit     ait_params  ]   DVB BlueBook A142 14 NOTE 1: See Table 1 NOTE 2: For org_id_part and app_id_part see [TS 102 812] NOTE 3: For digit and uric see [RFC 3986]   6.3.2 TV Locators A  locator  for  a  DVB  Service  or  service  component  can  be  a  full  dvb:  locator,  as  defined  in  table  1  in   clause  "6 specifc  forms  defined  in  table  3.   Table 3: Extended TV locators Locator Meaning dvb://current   The  service  currently  selected  by  the  application.   dvb://current.av   The  Audio  and  Video  being  presented  on  the  background  video   device   dvb://current.audio   The  Audio  being  presented  in  association  with  the  background   video  device   dvb://current.video   The  Video  being  presented  on  the  background  video  device   dvb://original   Originating  service  for  this  application  (place  of  birth)   NOTE: locator, as defined in [RFC 2838], may use the equivalent locator to reference the default audio and video component within the service.   6.3.3 Application Locator A  locator  for  an  application  in  the  current  service  can  be  identified  by  the  specific  forms  in  table  4.Only   applications  that  are  visible  in  the  application  database  using  the  current  service  filter  can  be  found  by   this  locator.   Selecting  this  locator  will  launch  the  application,  with  the  associated  parameters.  If  the  service   indicated  is  not  the  current  service,  a  service  selection  will  be  required.  After  successful  service   selection,  the  application  will  be  launched  with  the  associated  parameters.   Table 4: Application locator Locator Meaning dvb://current.ait/orgid.appid?param1=val1&...   An  application  in  the   service  currently  selected   by  the  application.   dvb://dvb_service_without_event.ait/orgid.appid?param1=val1&...  An  application  in  the   specified  service.     DVB BlueBook A142 15 6.3.4 AIT Locators The  root  directory  or  the  icon  representation  of  the  current  application  can  be  referenced  by  the   specific  forms  in  table  5.   Table 5: AIT locators Locator Meaning dvb://current.ait/app_root   The  root  directory  path  as  found  in  the  application  location   descriptor  for  the  application.   dvb://current.ait/app_icon   The  icon  found  in  the  application  icons  descriptor  for  the   application.     6.3.5 Exit Locator In  the  context  of  some  application  formats,  actioning  a  link  in  the  defined  element,  attribute  context   with  the  following  form  of  locator  shall  cause  an  application  to  terminate:   exit:   The  formal  specification  of  the  URL  is  given  in  the  BNF  in  table  6.   Table 6: Exit locator syntax exit_url   =   exit_scheme  *uric   exit_scheme   =   exit     Activating  such  a  link  shall  request  that  the  application  manager  move  the  current  application  into  the   specification  (see  [RFC  3986]).   6.3.6 Server Domain The  domain  part  of  an  application  format  specific  locator  shall  be  one  of:   The  domain  name  of  the  server  that  served  the  document  if  it  can  be  identified     NOTE:   Such  pages  cannot  therefore  be  in  the  same  domain  as  any  page  delivered  via  http.   Null  otherwise   DVB BlueBook A142 16 6.4 EPG, BCG and ESG Specific Locators 6.4.1 DVB Event Constraint For  use  in  EPGs  and  ESGs,  the  dvb_event_constraint  shall  be  encoded  as  defined  in  table  7.   Table 7: EPG/BCG/ESG specific DVB URL syntax dvb_event_constraint   =   event_id_mode  |  tva_id_only_mode  |  time_constraint   event_id_mode   =   event_id  [   TVA_id  ]  [  time_constraint  ]   tva_id_only_mode   =   TVA_id  [  time_constraint  ]   time_constraint   =   time_duration   TVA_id   =   1*hex   time_duration   =   start_time -­-­  duration   start_time   =   date  time     duration   =    hours    minutes   M [  seconds S ]   date   =   year  month  day   time   =   hours  minutes  [  seconds  ]   year   =   digitdigitdigitdigit   month   =   digitdigit   day   =   digitdigit   hours   =   digitdigit   minutes   =   digitdigit   seconds   =   digitdigit     The  format  of  the  time_duration  string  is  compatible  with  [ISO  8601].  Note  that  the  time  and  duration   -­‐  (cf.  clause  5.5.2  in  [ISO  8601]).   EXAMPLE:   20060908T091500Z PT00H30M00S   me  is  defined  with   respect  to  UTC.   6.4.2 Restrictions of EPG, BCG and ESG Specific Locators When  referencing  a  DVB  service,  the  DVB  locator  shall  be  restricted  like  so:   dvb://.[].   When  referencing  an  item  of  content  the  DVB  locator  shall  be  restricted  to  any  of  the  following:   DVB BlueBook A142 17 To  reference  an  item  of  content  via  an  event_id  carried  in  EIT:   dvb://.[].;;[~time_durati on]   To  reference  an  item  of  content  via  a  TVA_id  carried  in  EIT:   dvb://.[].;;;;[~time_durati on]   To  reference  an  item  of  content  via  a  TVA_id  carried  in  PES:   dvb://.[]..;;;;  [~time_duration]   To  reference  an  item  of  content  via  both,  an  event  id  and  a  TVA_id  carried  in  EIT:   dvb://.[].;;;;   [~time_duration]   To  reference  an  item  of  content  via  both,  an  event  id  and  a  TVA_id  carried  in  PES:   dvb://.[]..;;;;   [~time_duration]   To  reference  an  item  of  content  by  its  scheduled  time  for  broadcast:   dvb://.[].~time_duration   6.4.3 Locators in Metadata A  metadata  fragment  may  contain  a  DVB  locator  referencing  a  file  in  an  object  carousel.  When  this   occurs  and  the  file  is  delivered  in  the  same  object  carousel  as  the  metadata  service  delivering  the   metadata  fragment,  the  following  syntax  may  be  used  for  the  DVB  locator:   dvb:   This  path  shall  be  interpreted  as  being  an  absolute  path,  that  is  one  that  is  relative  to  the   ServiceGateway  for  the  object  carousel  carrying  the  metadata  service.   If  a  metadata  fragment  references  a  file  delivered  in  a  different  object  carousel  to  the  metadata  service   delivering  that  metadata  fragment,  the  following  syntax  shall  be  used  for  the  DVB  locator:   dvb://.[]..   {&}[$]   6.5 Resolution When  resolving  references  to  a  DVB  service,  the  numeric  identifiers  original_network_id,   transport_stream_id  and  service_id,  if  present,  shall  be  matched  against  the  corresponding  fields  in  the   SDT.   When  resolving  references  to  a  transport  stream,  the  numeric  identifiers  original_network_id  and   transport_stream_id  shall  be  matched  against  the  corresponding    fields  in  the  NIT.   DVB BlueBook A142 18 8 In  [RFC  5328],  DVB  defines  a  specific  Uniform  Resource  Name  (URN)  scheme  which  provides  a  general   naming  mechanism  intended  to  uniquely  identify  DVB  Schemas  and  Classification  Schemes.   8.1 Management urn:dvb Table  8   [RFC  5328].  A  register  of  assigned  DVB  URNs  can  be  found  in  [TR  102  679].     Table 8: URN Namespace Management URN Description urn:dvb:metadata Root of all DVB metadata URNs urn:dvb:metadata:schema All DVB generic schemas urn:dvb:metadata:cs All DVB classification schemes DVB Schemas organised by application area urn:dvb:metadata:xxx xxx replaced by application designation as registered with the DVB Project Office) 8.2 table  9  and  shall  be  registered  in   [TR  102  679]   Table 9: urn:dvb Naming Convention dvb_urn   =   urn:dvb:metadata:   : year  [   -­ revision  ]   classification_scheme   =   cs:"  cs_name   cs_name   =   CS   schema   =   [  application_designation   : :   application_designati =   lower_case+   on   year   =   digitdigitdigitdigit   revision   =   digit+   digit   =   "0"  |  "1"  |  "2"  |  "3"  |  "4"  |  "5"  |  "6"  |  "7"  |  "8"  |  "9"   lower_case   =   a z   upper_case   =   A Z   mixed_case   =   lower_case  |  upper_case         DVB BlueBook A142 19 Annex A (informative): Bibliography [RFC  791]   -­‐  Internet  Protocol  -­‐     USC    the  University  of  Southern  California   September  1981   [RFC  1737]   -­‐     K.  Sollins  /  L.  Masinter   December  1994   [RFC  1738]   "RFC  1738  -­‐  Uniform  Resource  Locators  (URL)"   T.  Berners-­‐Lee  /  L.  Masinter  /  M.  McCahill  (Editors)   December  1994   [RFC  2141]   -­‐     R.  Moats   May  1997   [RFC  2396]   -­‐     T.  Berners-­‐Lee  /  R.  Fielding  /  L.  Masinter   August  1998   [RFC  2717]   -­‐  Registration     R.  Petke  /  I.  King   November  1999   [RFC  2718]   -­‐      L.  Masinter  /  H.  Alvestrand  /  D.  Zigmond  /  R.  Petke   November  1999   [RFC  2732]   -­‐     R.  Hinden  /  B.  Carpenter  /  L.  Masinter   December  1999   [RFC  2838]   -­‐  Uniform  Resource  Identif   D.  Zigmond  /  M.  Vickers   May  2000   [RFC  3305]   -­‐  Report  from  the  Joint  W3C/IETF  URI  Planning  Interest  Group:  Uniform   Resource  Identifiers  (URIs),  URLs,  and  Uniform  Resource  Names  (URNs):     M.  Mealling  /  R.  Denenberg  (Editors)   August  2002   [RFC  3986]   -­‐     T.  Berners-­‐Lee  /  R.  Fielding  /  L.  Masinter   January  2005   DVB BlueBook A142 20 [DAVIC-­‐9]       Digital  Audio-­‐Visual  Council  (DAVIC)   1999   [MHEG-­‐UK]   Digital  Terrestrial  Television  MHEG-­‐   UK  Digital  TV  Group  (UK  DTG)   May  2003     DVB BlueBook A142 21 History Document  history                                   DVB BlueBook A142