URL proposal

From: Warner ten Kate (tenkate@natlab.research.philips.com)
Date: Fri, Nov 27 1998


Message-Id: <365E97F5.DD6C2F15@natlab.research.philips.com>
Date: Fri, 27 Nov 1998 13:15:49 +0100
From: Warner ten Kate <tenkate@natlab.research.philips.com>
To: www-tv@w3.org
Subject: URL proposal

Through this message I propose

To adopt the DAVIC specified general URL scheme as the 
general scheme to which TV Broadcast URLs must comply.

Wrt. the DAVIC specification I made the following adaptations:
- I added an explicit <time-period> field (semantics explained below).
  The field is optional and it corresponds to the DVB URL as 
  also specified by DAVIC.
- I made the <file> field optional to the <dir>-tree.

Both adaptations do not turn this scheme incompatible 
with the DAVIC scheme.


The proposed scheme reads: 

  <protocol>://<service>[;<time-period>][/<dir1>/.../<dirN>/[<file>]]

[square brackets] indicate optional fields.
<angle brackets> indicate fields; the name of the field written between 
  the brackets. The allowed character set is specified in RFC 2396.
The remaining characters are literal parts of the URI scheme.


The fields have the following semantics:

  <protocol> identifies that it concerns a TV Broadcast service and
             which access mechanism in that TV Broadcast system is 
             to be used.
             (Candidates are "dvb", "atsc", "tv".)
  
  <service>  identifies a particular channel service in the TV Broadcast 
             system. It can be a name (string) or a number (integer 
             sequence). The number corresponds to the ID of the service 
             as used by the TV Broadcast system identified by
             <protocol>.
  
  <time-period> identifies the time-period within which the resource
             will be available in the service identified by <service>.
             It is an optional field.
  
  <dir1>/.../<dirN> identify a hierarchical path to the resource.
             The semantics of that path is defined by the TV Broadcast
             system identified by <protocol>.
  
  <file>     identifies a resource in the service. 
  
  <dir1>/.../<dirN>/<file> is an optional part of the URI.
             when the <file> is omitted, the resource identified 
             is all the content available at and downwards from 
             the hierarchy level <dirN>.


Main motivation of this proposal is:

- The DAVIC scheme is the only URI scheme in the TV Broadcast area 
  existing which has been approved and consolidated by an official 
  standardization body. It is in use.

- It meets our requirements.

- It sets a framework, leaving open to specify various flavors 
  according to (application/system) specific details.



Warner.