Re: Don't put descriptive info in a URI, only identifying info

From: Warner ten Kate (tenkate@natlab.research.philips.com)
Date: Mon, Dec 21 1998


Message-Id: <367E9788.968ACDFF@natlab.research.philips.com>
Date: Mon, 21 Dec 1998 19:46:33 +0100
From: Warner ten Kate <tenkate@natlab.research.philips.com>
To: Dan Connolly <connolly@w3.org>
Cc: ietf-url@imc.org, www-tv@w3.org
Subject: Re: Don't put descriptive info in a URI, only identifying info

Dan Connolly wrote:
> 
> In a review of a draft of requirements for a TV URL scheme[1],
> I just noticed:
> |4.The URI scheme MUST support for OPTIONAL information
> |     from which it MUST be possible for a receiver to determine
> |     the time period(s) within which the resource can be retrieved
> |     from the (also resolved) location.
> 
> This conflicts with a design principle I hold about URIs,
> explained in my message to the uri list in Feb 1997[2]:
> 
> |If you're talking about "the document XYZ, which has title
> |ABC" then then ABC must not be part of the identifier. Because
> |you might want a reference ala "the document XYZ, which
> |has author Fred" to be recognized as the same resource.
> |
> |On the other hand, you might refer to a resource using
> |a restrictive clause: "the service ZZZ that started in 1996".
> |In this case, "the service ZZZ that started in 1995" is a
> |distinct resource. So the year is part of the URL.

Thanks for pointing to this.

Do I understand you correctly, that the first example URL
is wrong and the second example is right ?

In our model of a TV Broadcast stream we assume that the
content is scheduled by the service provider and the user
has no influence on that. The user accesses the stream(s) 
rather than the server at the uplink station.

For this discussion, there are two types of resources:
- TV channel
- TV program
A TV channel is the concatenation of TV programs. For 
example, "BBC-1" is a TV channel and "8 o'clock news"
is a TV program.

What does your comment imply when I want to express the 
location of the 8 o'clock news ?

- Is 8 o'clock news a further characteristic of BBC-1 (case 1)?
  It means TV programs should not be considered a resource ?
- Is 8 o'clock news a restrictive clause on BBC-1 (case 2)?
  It means temporal availability is allowed as part of the URL.

> 
> I started to (a) ask the editors of [1] to
> cite the URL scheme guidelines[3], and 

Will do.

> (b) remove requirement 4 since it conflicts. 

This has probably to do with the model above.
Do you have a suggestion how to deal with this ?
Should we adapt another model ? 


Warner.

--
Philips Research Labs. WY21 ++ New Media Systems & Applications
Prof. Holstlaan 4 ++ 5656 AA  Eindhoven ++ The Netherlands
Phone: +31 4027 44830
Fax:   +31 4027 44648    tenkate@natlab.research.philips.com