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RE: Review of quota-06

From: Jim Whitehead <ejw@soe.ucsc.edu>
Date: Thu, 17 Mar 2005 16:28:15 -0800
Message-Id: <200503180028.j2I0SK0k002067@services.cse.ucsc.edu>
To: <w3c-dist-auth@w3.org>

Julian,

> 01-C03 quota vs disk space
> <http://lists.w3.org/Archives/Public/w3c-dist-auth/2003JanMar/
> 0439.html>
> <http://lists.w3.org/Archives/Public/w3c-dist-auth/2003JanMar/
> 0460.html>
> <http://lists.w3.org/Archives/Public/w3c-dist-auth/2003OctDec/
> 0184.html>
> <http://lists.w3.org/Archives/Public/w3c-dist-auth/2003OctDec/
> 0193.html>
> 
> The spec says that servers may expose physical disk limits as quota.

In my reading of the -06 specification, I'm not able to see any mention of
this.

The only concern I see is that the definition of quota-available-bytes is
defined in terms of "disk space" available and not "storage space"
available. Then again, even storage media that aren't disks are typically
referred to as drives these days (e.g., "thumb drive" for RAM-based storage
sticks), so maybe it's not an issue.


> 04-C07, section 3, DAV:quota-available-bytes
> 
> <http://greenbytes.de/tech/webdav/draft-ietf-webdav-quota-05.h
> tml#rfc.section.3>
> 
>    "Support for this property is REQUIRED on collections, and 
> OPTIONAL on
>     other resources.  A server SHOULD implement this property for each
>     resource that has the DAV:quota-used-bytes property."
> 
> What's the motivation for the distinction? (same in section 4)

Seems to me the motivation is to ensure that collections know how much space
is available in their namspace, thereby providing clients an aggregated
understanding of available storage space associated with a particular
namespace.

It's not clear to me whether you object to this, or are seeking additional
clarification text.


> 
> 
> 04-C11, section 7
> 
>       "The total size of a collection, DAV:quota-used-bytes, is not
>        necessarily a sum of the DAV:getcontentlength properties for
>        resources stored in the collection."
> 
> Actually, it won't be in most cases I'm aware of. Please 
> either rephrase it (so this doesn't sound like an edge case) 
> or drop the point.
> 
> Update -06: It's now saying
> 
> "The total size of a collection, DAV:quota-used-bytes, may 
> not be a sum of the DAV:getcontentlength properties for 
> resources stored in the collection."
> 
> ...which isn't that different...

Let me suggest:

"Since there are many factors that affect the storage used by a set of
resources, including automatic compression, the size of associated metadata,
and server-inserted content (such as that created by PHP code) in the
on-the-wire representation of resources, clients are advised to not depend
on the value of DAV:quota-used-bytes being the sum of the
DAV:getcontentlength properties for resources contained by a collection."

 
> 05-C02, Section 4
> 
> <http://greenbytes.de/tech/webdav/draft-ietf-webdav-quota-05.h
> tml#rfc.section.4>
> 
> I think this property is "computed" (as defined in RFC3253), 
> and the spec should say so.

I agree. The DAV:quota-used-bytes is a "computed" property according to
RFC3253, and I agree it would be useful to explicitly state this.

I recommend adding the following sentence to the end of section 4, as a new
paragraph:

"This value of this property is computed (see Section 1.4.3 of [RFC3253] for
the definition of computed property). A 403 Forbidden response is
RECOMMENDED for attempts to write a protected property, and the server
SHOULD include an XML error body as defined by DeltaV [RFC3253] with the
<DAV:cannot-modify-protected-property/> precondition tag."


> 05-E01, section 1.2
> 
> <http://greenbytes.de/tech/webdav/draft-ietf-webdav-quota-05.h
> tml#rfc.section.1.2>
> 
> I'd move those parts that "import" terminology from 
> RFC2518/3253 into a 
> separate subsection ("Terminology"), and also refer to the def of 
> "computed" property (I think we need that later).

I mostly agree. I think the reference to RFC3253 for computed and protected
properties should go in Section 1.1, not in the "requirements" section.

So, I recommend deleting the following sentence from Section 1.2:

"This specification requires WebDAV because it requires PROPFIND support and
relies on the WebDAV definition of collections and properties, including the
definitions for live and protected properties (see section 1.4.2 of
[RFC3253] for the definition of protected properties)."

I recommend adding the following sentence to Section 1.1, as a new
paragraph.

"The definition of live property is provided in [RFC2518]. The definition of
protected and computed properties is provided in [RFC3253], Section 1.4."

- Jim
Received on Friday, 18 March 2005 00:31:37 GMT

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