RE: WRITE_DAV_PROP: Summary of consensus

Note though that updating getlastmodified is a significantly
more powerful operation than "touch".  Touch just says to act
as if you wrote the same content over again, i.e. the only
effect it has on getlastmodified is to reset it to the "current"
date.

On the other hand, updating getlastmodified lets you roll 
backward in time, thereby potentially breaking the various
caching schemes that depend on a one-way movement of the
getlastmodified value.  Note also that even if you intended
on just "rolling time forward", a client can't really get
the time "right", so it will set the time either "too early"
(i.e. earlier than "current") or "too late" (i.e. sometime
in the future).  Either of these situations can break the
caching uses of getlastmodified.  In particular, suppose 
you are writing a "too early" time ... if someone previously
wrote to the resource, which updated the getlastmodified
time to a time later than your "too early" time, 
then you will roll back the time (potentially breaking
some caching).  Now suppose you write a "too late" time.
Then someone does an update, which sets the getlastmodified
time to a "current" which is earlier than the time you set.
Again, a "time rollback" has occurred, and you can break
some caching. 

So, although I am in favor of "touch" functionality, I am
(strongly) against providing it via a writeable "getlastmodified".

Cheers,
Geoff
 

-----Original Message-----
From: Jim Amsden [mailto:jamsden@us.ibm.com]
Sent: Monday, April 16, 2001 4:27 PM
To: w3c-dist-auth@w3c.org
Subject: Re: WRITE_DAV_PROP: Summary of consensus


getlastmodified needs to be updatable to do a UNIX-like touch command. Sets
the modified date on a resource so dependent relationships are processed by
builders or make.



 

                    "Jim Whitehead"

                    <ejw@cse.ucsc.edu>       To:     "WebDAV WG"
<w3c-dist-auth@w3.org>                          
                    Sent by:                 cc:

                    w3c-dist-auth-requ       Subject:     WRITE_DAV_PROP:
Summary of consensus                   
                    est@w3.org

 

 

                    04/16/2001 03:20

                    PM

 

 




Let me see if I can summarize the points of consensus on this issue:

Consensus:

- protected (i.e. properties that MUST NOT be modifiable with PROPPATCH)
  creationdate
  getcontentlength
  getetag
  lockdiscovery
  supportedlock
  resourcetype

- not protected (i.e. properties that MUST be modifiable by PROPPATCH)
  displayname
  source

Still under discussion:

  getlastmodified
  getcontenttype
  getcontentlanguage

There are two open issues:

1. Changing get* properties requires the server to perform a property
lookup
when processing a GET method request, and this is a performance hit for
some
servers.

2. It is unclear why getlastmodified needs to be writeable.

Let's see if we can resolve these remaining issues over the next 1-2 days,
so we can wrap this one up.

- Jim

Received on Monday, 16 April 2001 16:51:19 UTC