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RE: Clarifications on RFC2518

From: Jim Whitehead <ejw@ics.uci.edu>
Date: Fri, 12 Mar 1999 11:12:58 -0800
To: Kevin Wiggen <wiggs@wiggenout.com>, WEBDAV WG <w3c-dist-auth@w3.org>
Message-ID: <001a01be6cbc$5807a4e0$d115c380@galileo.ics.uci.edu>

My comments are below, in <ejw> tags:

- Jim

--------------

1)  Properties.

On page 10 it reads: "The property namespace is flat; that is, no hierarchy
of properties is explicitly recognized ... it is not possible to define the
same property twice on a singe resource ... "

The spec then goes on  to give lots of examples with hierarchical
properties.  I assume from this that the examples on PROPFIND works as
follows:


<ejw>
A property has a name and a value.  The space of *names* is flat, but the
value of properties can be arbitrary XML, and hence as you and the spec.
point out, non-flat.

Your intuition is correct that it might very well be possible to have a
non-flat property namespace, with hierarchy in a property name indicating
XML sub-elements.  We did investigate this kind of capability, and
ultimately decided against it.  Some of the rationale is captured in:

http://lists.w3.org/Archives/Public/w3c-dist-auth/1998OctDec/0074.html
</ejw>



<R:bigbox>
    <R:BoxType> Box type A </R:BoxType>
</R:bigbox>

Is stored in the webdav server as property name <R:bigbox> with a value of
<R:BoxType> Box type A </R:BoxType>

Is this correct???


<ejw>
Actually, the value is:

<R:bigbox>
    <R:BoxType> Box type A </R:BoxType>
</R:bigbox>

That is, the value does explicitly include the <R:bigbox> and </R:bigbox>
tags.  This is because we adopt a convention of having the outermost XML
element of a property be the name of the property itself.

</ejw>


It seems to be correct especially when you have examples like

<Z:authors>
        <Z:Author> Jim Whitehead</Z:Author>
        <Z:Author> Roy Fielding</Z:Author>
<Z:authors>

which obviously violates the rules on page 10 unless the entire <Z:Author>
structure is stored as the value for <Z:authors>


<ejw>

In this case, the value of the property is:

<Z:authors>
        <Z:Author> Jim Whitehead</Z:Author>
        <Z:Author> Roy Fielding</Z:Author>
<Z:authors>

That is, there is one property, named <Z:authors>, with two sub-elements.

</ejw>

Assuming everything I have said is true (the only way I made sense of the
spec and its examples) then how should a webdav server respond to PROPFIND
when the property name is

<K:Foo/Bar>

Should it try to be intelligent and respond with
<K:Foo>
      <K:Bar> value </K:Bar>
</K:Foo>

or do the simple

<K:Foo/Bar> value </K:Foo/Bar>


The simple way also means that if <K:Foo> and <K:Foo/Bar> are defined,
propfind will return
<K:Foo> value </K:Foo>
<K:Foo/Bar> value </K:Foo/Bar>

instead of the XML you would expect.

I see the reasoning behind this if everything I wrote is true.  If it is,
maybe the spec should be changed to either give more concrete Property
examples up front, or remove so many hierarchical properties from the rest
of the examples.


<ejw>

If the property <K:Foo> is defined, its value will be returned by a
PROPFIND.  If the property <K:Foo/Bar> is defined, its value (that is, the
value of property named "K:Foo/Bar") will be returned.  Since there is no
hierarchy in DAV properties, the value of K:Foo is independent of the value
of K:Foo/Bar.

</ejw>


2)  I see a lot of discussion on COPY and MOVE and how they should work.  No
one (as far as I have read) has mentioned the fact that both do state "If a
resource exists at the destination and the Overwrite header is "T" then
prior to performing the copy the server MUST perform a DELETE with "Depth:
infinity" on the destination resource.

I can't think of any system (or utility) I have used that does this. Most
would overwrite the file if it already existed but not destroy any other
files which might have been there.

Thus

COPY

foo--            TO          foo--
     |                                |
     -text.htm                   - list.htm

Gives the directory foo with simply text.htm in it instead of what I
expected which is foo with BOTH list.htm and text.htm

I looked in the FAQ and old emails for answers and couldn't find this
mentioned...

<ejw>

The rationale here was to make sure that the copy and move for Depth 0 had
the same semantics as a copy/move for Depth infinity.  Since a user will not
typically be interacting directly with the protocol, and since mechanisms
exist to do other semantics if desired, a client could expose other
semantics to their users via its user interface.

</ejw>

- Jim
Received on Friday, 12 March 1999 14:23:11 GMT

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