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RE: Review of ordering draft, version 05

From: Julian Reschke <julian.reschke@gmx.de>
Date: Thu, 13 Feb 2003 21:25:14 +0100
To: "Webdav WG" <w3c-dist-auth@w3c.org>
Message-ID: <JIEGINCHMLABHJBIGKBCGEIOGHAA.julian.reschke@gmx.de>

Hi.

I have adressed some of Lisa's issues, in particular:

- how to interpret the DTD fragments [1]
- reference to RFC3253 pre/postcondition definition [2]

I've also tried to clarify the relation to versioned collection ([3]).

To those who revieved the 05 draft: please check out the current version
(all changes are highlighted) -- I intend to submit this draft as "last
call" version early next week.

Julian


[1]
<http://greenbytes.de/tech/webdav/draft-ietf-webdav-ordering-protocol-latest
.html#rfc.section.1>
[2]
<http://greenbytes.de/tech/webdav/draft-ietf-webdav-ordering-protocol-latest
.html#rfc.section.3>
[3]
<http://greenbytes.de/tech/webdav/draft-ietf-webdav-ordering-protocol-latest
.html#rfc.section.9>

--
<green/>bytes GmbH -- http://www.greenbytes.de -- tel:+492512807760

> -----Original Message-----
> From: w3c-dist-auth-request@w3.org
> [mailto:w3c-dist-auth-request@w3.org]On Behalf Of Lisa Dusseault
> Sent: Saturday, February 08, 2003 6:46 PM
> To: 'Julian Reschke'
> Cc: Webdav WG
> Subject: Review of ordering draft, version 05
>
>
>
>
> Since we're getting close to last call on the ordering draft, I reviewed
> it all again (it's been years since I did so before).  Here are all my
> comments.
>
> Section 3:
> "This document uses the terms "precondition" as "postcondition" as
>    defined in [RFC3253]. "
>
> Should be "and", not "as"
>
> I don't think it's sufficient to just import the definitions of
> precondition and postcondition. These are concepts that can clarify
> what's going on, but unless it's accompanied by really plain English,
> future readers of the specification won't be able to extract the
> information they need. Long-timer WG participants may know the meaning,
> but I'm learning more and more about people who never come to the
> working groups, who may only read little pieces of our specifications
> (e.g. a developer who doesn't usually do protocol implementation but is
> assigned to fix a bug).  Server implementors won't bother verifying
> whether some condition is one they have to enforce, or simply ignore it.
> I strongly recommend including the standard MUST/MAY/SHOULD language
> that specification readers are familiar with, particularly in the
> postconditions which are not just error code definitions but also
> specify behavior.
>
> As an example, I'll jump ahead to the first precondition and
> postcondition in section 5.1.  I'm not even sure what they mean, but
> I'll try to guess in order to restate them. Here's what I'd like to see:
>
>  Additional Preconditions:
>
>       (DAV:ordered-collections-supported): Error used when the client
> attempts to create an ordered collection, if the server does not support
> the creation of ordered collections in this namespace.
>
>   Additional Postconditions:
>
>       (DAV:ordering-type-set): The server MUST set the ordering-type
> property on the new resource to the value specified in the Ordering-Type
> header by the client. If it cannot, this error should be used.
>
> That's just a sample; all of the postconditions and preconditions need
> to be full sentences explaining what must or may happen.
>
> Section 5.1:
> "If the Ordering-Type header is not present, the collection will be
> unordered."
>
> "Will be" is ambiguous standards language.  It implies MUST but doesn't
> really require anything.  "... the server MUST create the collection as
> unordered" is one possibility. However, it's fine to say "... the
> collection MAY be created as unordered" if we want to give servers the
> freedom to make new collections ordered by default.
>
> Section 5.1: I don't see how the ordering-type-set postcondition can be
> implemented. How can the server tell the difference between an ordering
> type that it must support, or an ordering type that it's not supposed to
> know about but just advertise?
>   Or is the server just supposed to set the value, period?  If that's
> the case, then why isn't this simply a MUST requirement, rather than a
> postcondition?
> I suspect I don't really understand the ordering-type-set postcondition,
> thus it probably just has to be explained more in the specification.
>
>
> Section 6.1
> The "segment" definition in BNF is imported from RFC2396.  But that
> definition says that a segment can contain a "param":
> 	RFC2396
> 	  "segment       = *pchar *( ";" param )"
>
> What would the param be or mean?  I suspect we'll have to define our own
> here.
>
> " The server MUST insert the new member into the ordering at the
>       location specified in the Position header, if one is present (and
>       if the collection is ordered)."
>
> What does the "one" refer to in "if one is present"?  I think this means
> "If the collection is ordered and a new member is inserted with the
> Position header, the server MUST insert the new member into the ordering
> at the location specified in the header."
>
> " (DAV:collection-must-be-ordered): the target collection must be
>       ordered."
>
> Does this mean that the request to PUT a resource *fails* if the client
> includes a Position header and the collection isn't ordered?  That's
> expensive for a client to have fail.  I don't know if that's what client
> implementors are going to want to happen.
>
> "    (DAV:segment-must-identify-member): the referenced segment must
>       identify a resource that exists and is different from the affected
>       resource."
>
> Again, does this mean the server MUST fail the PUT request if the
> segment in the Position header doesn't exist?
>
> "     (DAV:position-set): the newly created collection member was
>       created at the specified position."
>
> Shouldn't the server always create the new member at the specified
> position (a MUST)? Under what circumstances would this ever not happen?
>
> Specification organization: how about putting the Position and
> Ordering-Type header definitions in their own sections, titled "Position
> Header" and "Ordering-Type Header". That makes it easier for people to
> use the specification as a reference.
>
>
> Section 7.
>
> "     <!ELEMENT orderpatch (ordering-type?, ordermember*) >"
>
> This definition makes the orderpatch element (thus the ORDERPATCH
> request body) non-extensible unless we say otherwise.  We could put in
> the "elements not understood by the server MUST be ignored" language, or
> redefine certain elements as
>
>       <!ELEMENT orderpatch (ordering-type?, ordermember*, ANY) >
>
> We need to say that the list of <ordermember> elements in the orderpatch
> body is itself order-dependent -- I believe the server must process them
> in the order they appear, first to last.  Actually, this is specified in
> section 7.1 under the example, but it should be said in section 7.
>
> "      (DAV:orderding-modified): if the request body contained
>       DAV:ordermember elements, the ordering of internal member URIs in
>       the collection identified by the request-URI has been changed
>       based on instructions in the DAV:ordermember elements."
>
> Isn't this a simple MUST rather than a postcondition?  "The server MUST
> order internal member URIs in the collection identified by the
> request-URI based on instructions in the DAV:ordermember elements in the
> ORDERPATCH request body." Under what conditions would this
> ordering-modified error be returned to the client?
>
> Section 7.2.
>
> This example shows what happens if the fourth <segment> element in the
> request body does not name a valid segment.  By analogy, I can see what
> would be returned if the second <segment> element were invalid. However,
> I'm not clear what would happen if the first or third <segment> element
> were invalid.  What would be returned in the <href> element in the error
> response?
>
> "Because ORDERPATCH is an atomic method, the request to
>    reposition nunavut.desc (which would otherwise have succeeded) failed
>    as well, but doesn't need to be expressed in the multistatus response
>    body."
>
> One of the things we've learned from RFC2518 interoperability is that's
> not necessarily true. When a server does a MOVE on a collection, the
> client has a hard time figuring out which things moved and which didn't.
> Some responses have the failed dependency error, others don't.  Should
> we consider being more specific here? The server could simply include a
> 424 Failed Dependency error for each ordering that failed because of the
> atomicity of the method.
>
> Section 9.1.
>
> "The property DAV:version-controlled-binding-set ([RFC3253], section
>    14.2.1) records the set of version-controlled bindings in the
>    collection. For ordered collections, the DAV:version-controlled-
>    binding elements MUST appear in the ordering defined for the checked-
>    in ordered collection."
>
> This is true only for working collections when versioned collections are
> supported. At a minimum, change to:
>
> "The property DAV:version-controlled-binding-set ([RFC3253], section
>    14.2.1) records the set of version-controlled bindings in a
>    working collection (part of the versioned collections feature).
>    For an ordered working collections, the
>    DAV:version-controlled-binding elements MUST appear in the ordering
>    defined for the associated checked-in ordered collection."
>
> Doesn't that mean that the user can't reorder a collection that they've
> checked out into a working collection?
>
> Section 10 (Discovery).
>
> "  Furthermore, RFC 3253 [RFC3253] introduces the live properties
>    DAV:supported-method-set (section 3.1.3) and DAV:supported-live-
>    property-set (section 3.1.4). Servers MUST support these properties
>    as defined in RFC 3253."
>
> Do you mean that any server that supports this specification must
> support these two RFC3253 properties as well? If so, that could be made
> a little more clear like this:
>
> "  Furthermore, RFC 3253 [RFC3253] introduces the live properties
>    DAV:supported-method-set (section 3.1.3) and DAV:supported-live-
>    property-set (section 3.1.4). Servers supporting ordered-collections
>    MUST support these properties as defined in RFC 3253 even if the
>    server does not support any RFC3253 features."
>
> Section 16. Acknowledgements
>
> "Lisa Lippert" was me, but my name is now "Lisa Dusseault" again...  I'd
> much prefer to be listed as Dusseault!
>
> Lisa
>
>
Received on Thursday, 13 February 2003 15:26:01 GMT

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