RE: Where are we?

From: dean blackketter (
Date: Tue, Oct 12 1999

Message-Id: <>
Date: Tue, 12 Oct 1999 08:10:43 -0700
To: Harald Tveit Alvestrand <>, Dan Zigmond <>,
From: dean blackketter <>
Subject: RE: Where are we?

At 10:29 AM 10/11/99 -0700, Dan Zigmond wrote:
>One of my colleagues, Dean Blackketter, has been working on a system for
>describing time periods using the URI fragment syntax.  This seems like a
>fairly natural extension of the notion of fragment into the time domain,
>since in a sense what you're asking for is a way to specify that fragment of
>a television stream that contains the material broadcasted at a particular
>I'll let Dean post a more complete specification, but the basic syntax uses
>ISO-8601 time formats and looks something like this:

I'll post the complete description in a day or so. I'm currently swamped 
with some emergency bug-fixing, but I had a couple of notes...

>which represents whatever is on PBS between 1PM and 1:30 today.  I've made
>this unnecessarily long just as an example; in 8601 you can drop the
>trailing zeros, and the date itself is optional.  I think 8601 is a pretty
>complete and flexible representation of time, so leveraging it makes the
>problem a lot simpler than having to make something up.
>As has been pointed out, this is a fundamentally different problem than URIs
>for specific programs on television, which should be independent of both
>network and time.

At 10:22 AM 10/12/99 +0200, Harald Tveit Alvestrand wrote:
>Seems logical.
>two things to note:
>- dropping the date is unwise in the extreme unless you want the syntax to
>   mean "every day" - which is an extension I would very much like to avoid.
>   see below.

Yes.  Actually, ISO-8601 doesn't have a date-dropped form, but our 
implementation does as an extension.  A dropped date indicates the next 
matching time in the next 24 hours.  It's a compact form that's useful for 
referring to a program that's on in same evening.

>- On the principle of "all URLs escape the context for which they were
>   created", I would VERY much like to ask for the mandatory inclusion of
>   timezone. You never know who is going to try to watch this, via what 
> medium.
>So your example (also including a feed identifier) would become
>and be unambiguous whether it was looked up in Texas or California.

That's right.  But we also allow for the dropping of the zone indicator 
("+0500" in your example) to be equivalent to "+0000" to mean that the time 
is UTC.  So your example could be compacted (by removing trailing zeros, 
optional hyphens and folding the zone into the time in UTC) as:

And still be unambiguous.

I'll post a complete description of the syntax we are using as soon as I can.