W3C home > Mailing lists > Public > w3c-dist-auth@w3.org > January to March 1999

FW: [Moderator Action] ACP Issue YG-7

From: Jim Whitehead <ejw@ics.uci.edu>
Date: Tue, 23 Mar 1999 12:06:47 -0800
To: WEBDAV WG <w3c-dist-auth@w3.org>
Message-ID: <000d01be7568$aea12ec0$d115c380@galileo.ics.uci.edu>
Caught by the spam filter.  A request is in to add jdavis@coursenet.com to
the accept2 list.

- Jim

-----Original Message-----
From: Jim Davis [mailto:jdavis@coursenet.com]
Sent: Tuesday, March 23, 1999 12:00 PM
To: w3c-dist-auth@w3.org
Subject: [Moderator Action] ACP Issue YG-7


YG-7 is "Do references to collections have to provide references for all
the members of the collection? If one creates a reference to a collection
is one also required to create references to all the members of that
collection? I suspect the answer is yes but this is not clear from the
spec. If one creates a reference to a collection, MUST a GET on collection
members accessed through that reference succeed? In other words, by
creating a reference to a collection is one required to create reference to
its entire tree? (Request for clarification not for change.) Section 4.4.1"

Well, no and yes.  If A is a reference to collection C, which contains
member Q, then a client request on A/Q ishould succeed, but A/Q is *not* a
reference.  Its resourcetype is not DAV:reference.  See 4.16  of the 03
draft.

Here's the design rationale.

Question 1: should references be allowed to point to a collection at all?
 Yes.
   1. Server can't prevent it for redirect references
   2. it's useful
   3. it's meaningful.

Question 2: in that case, what does A/Q mean?
 alternatives:
   1. 404 not found
        con: then what use is the reference to the collection?  The client
could have done PROPFIND on A, would expect it to have members, so how can
webDAV then refuse requests on those members?
   2. follow the reference A.
       if A is redirect, then return 302 P/Q
       if A is direct, then just follow to P/Q (server side)

There is some controversy about the redirect case.  The server has no way
to know that the target is in fact an resource such that P/Q makes sense.
 So you could argue that redirect should not be allowed, but the arguments
against this are:
 1) the client could only have obtained the URL A/Q in the first place
either because P acted like a collection last time it was visited, or
  2) the client was just randomly entering URL strings.

Note that the meaning of 302 is "moved temporarily", not permanently.  So
it's reasonable for a client  to have done the following:
  PROPFIND A (gets 302 to P)
  PROPFIND P (finds Q)
  PROPFIND A/Q (because 302 does not mean "use P/Q forever")

Note also that RFC 2396 section 5 sanctions hierarchic resource names in
general, so it's reasonable to do such "URI arithmetic" on non-HTTP URIs

Question 3: what about No-Passthrough on such a URL A/Q
 Answer:   Since A/Q isn't a reference, the No-Passthrough is of no
consequence (unless the target P/Q is itself a reference).

Question 4: When one does a PROPFIND with non-zero Depth on A, what are the
URLs in the href elements returned?
 1. A/Q
 2. P/Q
 3. Q (relative URLS)

while choice 1 seems (at first) like it might be a hassle, but it isn't,
since the URL replacement only has to happen in one place (the front of the
URL).  In general, at least for file-system based WebDAV servers, it will
rarely happen that the root of the file system will also be the root of the
WebDAV namespace, so such servers will have to perform some string
operations on the front of the URL pathname anyway.

choice 2 seems to violate laws of webDAV namespaces.  It would be weird if
collection A had a direct member whose URL was such that it did not appear
(on syntactic grounds) to be a member of A.

choice 3 may or may not be allowed.  We need an expert ruling whether href
can be relative or must be absolute.  If it's legal, then it's a valid
choice as well.

please reply to jrd3@alum.mit.edu, despite the Reply-To address in the
header.
Received on Tuesday, 23 March 1999 15:14:54 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 2 June 2009 18:43:49 GMT