W3C home > Mailing lists > Public > uri@w3.org > April 2003

Re: temporal fragments

From: John Cowan <cowan@mercury.ccil.org>
Date: Mon, 7 Apr 2003 08:34:51 -0400
To: Silvia.Pfeiffer@csiro.au
Cc: uri@w3.org
Message-ID: <20030407123451.GZ26938@ccil.org>

Silvia.Pfeiffer@csiro.au scripsit:

> Indeed, when looking at rtsp and media streamed over it, a fragment 
> specification in a URI pointing to some media will certainly flag to the 
> user that the streaming will start at that offset. An offset in rtsp 
> makes sense to be specified in two ways:
> - the traditional "named" way. This is analogous to the specification of
>   <a name="offset"...> in html which gets identified in a URI as
>   http://...#offset. Such markers also exist on media files; e.g.
>   QuickTime files allow for chapter markers. Specifying them through
>   rtsp://...video.mov#offset expresses the expectation to stream from
>   that offset. As rtsp streams can be volatile (and thus there is no
>   "retrieved" representation of them), the offset interpretation must be
>   performed on the server side and not the client side.
> - the "timed" way that we proposed as in rtsp://...video.mov#@npt=241.6.
>   There is no analogy with html here as the specification of a character
>   offset into a html file does not make sense to most people. However,
>   with time-continuous data, this makes sense as the timing is an
>   inherent property of a time-continuous resource. Therefore our
>   suggestion to handle time offsets in the same way as named offsets.

[much snipped]

This is rather densely written, but if I understand the issue (i.e. I am
not too dense myself), then what it seems to me that you want is in fact
the query (?...) rather than the fragment (#...) syntax.  Queries unlike
fragments are passed to the server by general URI dereference, to handle
as it pleases.  The query is part of an absolute URI, not merely of a URI
reference, and its meaning can only be understood in the context of
everything to the left of it.  Many schemes (ftp, telnet, gopher, e.g.)
don't do anything useful with queries, but they are always supported

AFAIK nothing prevents you from defining with the rstp scheme a universal
meaning of queries, as in the mailto: protocol where queries of the form
?foo=bar&baz=quux mean to generate header lines "Foo: bar" and "Baz: quux".

John Cowan           http://www.ccil.org/~cowan              cowan@ccil.org
To say that Bilbo's breath was taken away is no description at all.  There
are no words left to express his staggerment, since Men changed the language
that they learned of elves in the days when all the world was wonderful.
        --_The Hobbit_
Received on Monday, 7 April 2003 08:36:04 UTC

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