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Re: Hierarchical URLs and Collections

From: Slein, Judith A <JSlein@crt.xerox.com>
Date: Tue, 18 Aug 1998 12:13:02 -0400
Message-ID: <201BB34B3A73D1118C1F00805F1582E8B76C42@x-wb-0128-nt8.wrc.xerox.com>
To: "'WebDAV'" <w3c-dist-auth@w3.org>
Cc: "Falkenhainer, Brian" <Brian_Falkenhainer@mc.xerox.com>, "Garnaat, Mitchell" <MGarnaat@crt.xerox.com>
Brian summarized his original issue to me very succinctly this morning:

WebDAV equates semantic containment with syntactic containment in a URL
path.  It assumes that any semantic containment relationships will be
reflected in the URL path.  Document repositories typically do not make
this assumption.  

In fact, repositories strongly prefer not to make this assumption.  They
don't want to use location as a means of referring to objects they
control, since location can change; they want to use an identifier that
is guaranteed not to break.

What we need to assess is whether making the assumption that semantic
containment is reflected in the syntax of the URL has caused any serious
problems in WebDAV.

Jim Whitehead pointed out that document repositories can still construct
valid WebDAV URLs that separate semantic containment from the URL.  They
simply show a flat namespace to the world in the URL, and maintain the
containment relationships separately.

John Turner has also pointed out that the repository can map its flat
namespace into one that embodies the semantic containment relationships
in URLs.  This practice presumably is offensive to repository designers
who so carefully avoided it in developing their products.

Do clients care whether the URL embodies semantic containment
relationships or not?  Presumably not when they are navigating downward,
since they will use PROPFIND to do that.  But if they want to navigate
upward in the containment hierarchy, WebDAV provides no standard way to
do so except by parsing the URL.

I suspect this is an oversight in WebDAV that may have resulted from
assuming containment relations would be visible in the URL syntax.
Unless it can be remedied, it means that repository vendors MUST
construct URLs that show the semantic containment relationships.

-- Judy

Judith A. Slein
Xerox Corporation
jslein@crt.xerox.com
(716)422-5169
800 Phillips Road 105/50C
Webster, NY 14580
Received on Tuesday, 18 August 1998 12:14:28 GMT

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