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Re: DELETE in WebDAV Collections

From: Roy T. Fielding <fielding@kiwi.ics.uci.edu>
Date: Fri, 21 May 1999 18:51:50 -0700
To: "Geoffrey M. Clemm" <gclemm@tantalum.atria.com>
cc: w3c-dist-auth@w3.org
Message-ID: <9905211851.aa24357@paris.ics.uci.edu>
>	    The resource is the conceptual mapping to an entity or set of
>	    entities, not necessarily the entity which corresponds to that
>	    mapping at any particular instance in time.
>This makes it even more inclusive, since "not necessarily" doesn't rule
>out anything, it just extends it.  Of course "conceptual mapping" does
>open up the barn door pretty wide (:-).
>            Thus, a resource
>	    can remain constant even when its content---the entities to
>	    which it currently corresponds---changes over time, provided
>	    that the conceptual mapping is not changed in the process.
>This is an intriguing statement.  I'm not sure what "remain constant"
>is supposed to mean or imply.  And again, what is a "conceptual mapping"?

It is a mapping from a concept to a representation of that concept.

>   Plus, the definition is very
>   careful to note that a resource is a "conceptual mapping to an entity" but
>   is not necessarily the actual entity itself.  In the file system case, this
>   means a resource is a conceptual mapping to a file, not the file itself.
>Well, not really.  It says that it is "not necessarily" the actual entity
>itself, but this doesn't rule out that the resource being the file itself.

That is because some concepts may be equivalent to "this exact file".
If that is the concept being mapped, then the resource will indeed be a
file, and thus the "not necessarily".  file URLs are an example of such.

The goal of the definition of resources is to make it possible for an
author to identify any possible resource via a URI, without necessitating
a change of the URI every time the representation of that resource changes.
In other words, we want the Uniform Resource Identifier to identify the
resource that corresponds to the concept desired by the author when they
created the link.  If the author wants to identify a fixed representation
(such as a revision of a file), then they will want to refer to a resource
that corresponds to that fixed representation.  It is thus natural to have
some URI that refer to more abstract concepts and others that refer to
concrete concepts.  It does make authoring rather more complicated, but
at least it is for a good cause.

Received on Friday, 21 May 1999 21:53:42 UTC

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