W3C home > Mailing lists > Public > public-ws-resource-access@w3.org > April 2009

RE: issue 6432 - yet another proposal

From: Christopher B Ferris <chrisfer@us.ibm.com>
Date: Tue, 21 Apr 2009 06:10:14 -0600
To: "Chou, Wu (Wu)" <wuchou@avaya.com>
Cc: "Asir Vedamuthu" <asirveda@microsoft.com>, "Li, Li (Li)" <lli5@avaya.com>, public-ws-resource-access@w3.org, public-ws-resource-access-request@w3.org
Message-ID: <OF6EDB786E.F7D4DA24-ON8525759F.003CACC7-8525759F.0042DADC@us.ibm.com>
Wu,

This does not help me understand what Push means, and given that it is 
defined as the default/implied
mode, that understanding seems to be fundamental to the correct 
implementation of the specification. 
A specification is supposed to provide an implementer with all of the 
information needed to produce an 
implementation. Clearly, there is something missing here because I have no 
idea what "simple asynchronous 
messaging" means. See Bob's note.

As to your point that @Mode was intended to enable resource constrained 
devices to effectively bypass use
of some of the more advanced WS-* features, please help me understand 
which of these features is needed to 
implement Push. 

Even in my most fevered dreams about what Push means, I fail to perceive a 
need for anything more
advanced (beyond what WS-E already prescribes) than WS-Policy (to 
advertise that Push is supported, 
whatever that means) which requires almost no code on the part of the sink 
(other than to return the policy 
when asked). The policy itself can be quite compact. As for the source, it 
requires a small amount of code to 
ask for the policy and a trivial amount of code to affect policy 
intersection to determine compatibility of the 
two policies. The source could support a single policy alternative, 
reducing the complexity of the intersection 
code (which isn't very complex in any event). 

You could even define a meta policy assertion that collapsed the semantic 
of a given policy alternative to a 
single assertion type such that intersection involved comparison of a 
single XML element with some static
QName which is effectively what @Mode is attempting to do (but without an 
underlying framework).

Even if I used WS-Man's PushWithAck as an example @Mode, my experience 
tells me that the implementation 
required to affect the behavior described (which is, again, somewhat 
hand-wavy in its specificity, but I digress) 
would not be much less than that required to implement a stripped down 
version of WS-RM (to affect acks) and there
is nothing in the WS-RM spec to preclude the sink from simply discarding 
and not acknowledging events that are not 
sequential in their order so as to affect in-order delivery (which is what 
PushWithAcks is attemping to achieve)
without requiring that the constrained device maintain a queue of 
unprocessed messages while it waits for a gap to 
be filled.

I could go on, but suffice to say that we designed WS-RM and many of the 
other WS-* specs such that
even in the case of resource constrained devices, the protocols could be 
effectively and efficiently implemented
to yield the desired functionality. If you have specific feedback that 
this is not the case, I am sure that the
relevant TC/WGs would be interested. 

Here's my main point. When there are more ways to affect the same 
functionality, there is less interoperability.

It is that simple. 

The W3C WS-Policy WG produced 2 Recommendations that enable a means of 
enabling two endpoints to 
communicate their capabilities and requirements to one another and 
determine their mutual compatibility.
I maintain that @Mode is yet another, albeit limited, means of 
accomplishing the same. 

Why do we need two?

Cheers,

Christopher Ferris
IBM Distinguished Engineer, CTO Industry Standards
IBM Software Group, Standards Strategy
email: chrisfer@us.ibm.com
blog: http://www.ibm.com/developerworks/blogs/page/chrisferris

phone: +1 508 234 2986





From:
"Chou, Wu (Wu)" <wuchou@avaya.com>
To:
Christopher B Ferris/Waltham/IBM@IBMUS
Cc:
"Asir Vedamuthu" <asirveda@microsoft.com>, "Li, Li (Li)" <lli5@avaya.com>, 
<public-ws-resource-access@w3.org>, 
<public-ws-resource-access-request@w3.org>
Date:
04/21/2009 01:19 AM
Subject:
RE: issue 6432 - yet another proposal
Sent by:
public-ws-resource-access-request@w3.org



Christopher,
 
My previous post was to point out, in addition to use other WS-*, WS-E 
provides one simple solution in @Mode that can be used to deal with such 
cases without requiring several other WS-* standards. Mode is implemented 
in current WS-E implementations and used extensively in deployed 
applications. 
 
If "@Mode tells me nothing", then please don't use it. You can use 
multiple WS-*  to address the problem. But on resource limited devices and 
for real-time communication, a simple and efficient solution without 
dependency on multiple WS-* has its value. 
 
Sorry, given the limited resources (cpu, memory) on the device and the 
number of WS-* to implement for the required functions, it is absurd and 
we should not make it even more absurd by mandatorily requiring more and 
more WS-* for something as simple as eventing.
 
Thanks,
 
- Wu Chou.
 
Wu Chou, IEEE Fellow, Ph.D. | Director |Avaya Labs Research | AVAYA | 233 
Mt. Airy Road| Rm. 2D48 | Basking Ridge, NJ 07920 | Voice/Fax: 
908-696-5198 / 908-696-5401 | wuchou@avaya.com 
From: Christopher B Ferris [mailto:chrisfer@us.ibm.com] 
Sent: Monday, April 20, 2009 8:51 AM
To: Chou, Wu (Wu)
Cc: Asir Vedamuthu; Li, Li (Li); public-ws-resource-access@w3.org; 
public-ws-resource-access-request@w3.org
Subject: RE: issue 6432 - yet another proposal

Wu, 

@Mode tells me nothing. The "Push" mode is especially vague in a 
completely unspecified and hand-wavy sort of way. The alluded to, but 
underfined "Wrap" mode is completely orthogonal to Push as it only speaks 
to the format of the event, not the means by which it is 
delivered/transferred from source to sink. 

/s:Envelope/s:Body/*/wse:Delivery/@Mode 
The delivery mode to be used for notification messages sent in relation to 
this subscription. Implied value is "
http://www.w3.org/2009/02/ws-evt/DeliveryModes/Push", which indicates that 
Push Mode delivery should be used. See 2.2 Delivery Modes for details. 
If the event source does not support the requested delivery mode, the 
request MUST fail, and the event source MAY generate a 
wse:DeliveryModeRequestedUnavailable fault indicating that the requested 
delivery mode is not supported. 
Not much detail there. It tells me to go to section 2.2 for details... 
let's see what that has to say. (Oh, note also that the spec only suggests 

that an endpoint MAY respond with a wse:DeliveryModeRequestedUnavailable 
fault. WOW is that ever helpful. Negotiation is almost guaranteed. NOT. 
Note that faults are _generated_. They are not necessarily transferred, 
and certainly not necessarily transferred to the origin of the message 
that triggered the fault to be generated. Using faults as a means of 
negotiation is, IMO, a poor design choice.) 

On to section 2.2, which I will quote in its entirety so that no one 
complains that I took anything out of context: 

2.2 Delivery Modes 
While the general pattern of asynchronous, event-based messages is 
extremely common, different applications often require different event 
message delivery mechanisms. For instance, in some cases a simple 
asynchronous message is optimal, while other situations may work better if 
the event consumer can poll for event messages in order to control the 
flow and timing of message arrival. Some consumers will require event 
messages to be wrapped in a standard "event" SOAP envelope, while others 
will prefer messages to be delivered unwrapped. Some consumers may require 
event messages to be delivered reliably, while others may be willing to 
accept best-effort event delivery. 
In order to support this broad variety of event delivery requirements, 
this specification introduces an abstraction called a Delivery Mode. This 
concept is used as an extension point, so that event sources and event 
consumers may freely create new delivery mechanisms that are tailored to 
their specific requirements. This specification provides a minimal amount 
of support for delivery mode negotiation by allowing an event source to 
provide a list of supported delivery modes in response to a subscription 
request specifying a delivery mode it does not support. 
This specification defines a single delivery mode, Push Mode, which is 
simple asynchronous messaging. 
As an example of a possible extension, a feature may allow a subscriber to 
request that event messages be "wrapped" in a standard message. This 
feature is requested by specifying a new delivery mode, e.g. 
http://www.w3.org/2009/02/ws-evt/DeliveryModes/Wrap, in the Subscribe 
request. Use of this delivery mode would indicate that notification 
messages should be "wrapped". Similarly, this approach could be 
generalized to allow the subscriber to provide other information regarding 
their preferences for notification message delivery. 

Would someone please explain where the precise definition of "simple 
asynchronous messaging" is specified? The very concept of "simple 
asynchronous messaging" is an oxymoron. Whatever it is, it isn't simple. 
The subject of what constitutes "asynchronous messaging" has been the 
source of much debate within the industry for years. It basically nets out 
to "it depends on your perspective what that term means" [1]. I could dig 
up reams of references from the WS-A WG discussion of the subject. 
Certainly, a three word phrase does not do the subject justice. Someone 
needs to define precisely what this mode means from an implementation 
perspective or interop is more likely than not to be non-existant. 

My point in my previous post was intended to point out that the WS-* 
community _has already done this work_. It is manifested in the WS-Policy 
1.5 Recommendations, and in the policy assertion vocabularies that have 
been developed for it, including WS-Addressing. Why should WS-E, a 
specification being developed by the very same group that is developing 
WS-MEX which builds off of WS-Policy (amongst other specs) to further 
enhance this system, clinging unnecessarily to its own ill-defined and 
ill-conceived solution to the same problem domain? 

For anyone to claim that this redundant and ill-defined feature needs to 
be retained to preserve compatibility with previous implementations is 
absurd. 

[1] http://lists.w3.org/Archives/Public/www-ws-arch/2003May/0014.html 

Cheers,

Christopher Ferris
IBM Distinguished Engineer, CTO Industry Standards
IBM Software Group, Standards Strategy
email: chrisfer@us.ibm.com
blog: http://www.ibm.com/developerworks/blogs/page/chrisferris

phone: +1 508 234 2986 




From: 
"Chou, Wu (Wu)" <wuchou@avaya.com> 
To: 
Christopher B Ferris/Waltham/IBM@IBMUS 
Cc: 
"Asir Vedamuthu" <asirveda@microsoft.com>, "Li, Li (Li)" <lli5@avaya.com>, 
<public-ws-resource-access@w3.org>, 
<public-ws-resource-access-request@w3.org> 
Date: 
04/18/2009 01:27 AM 
Subject: 
RE: issue 6432 - yet another proposal 
Sent by: 
public-ws-resource-access-request@w3.org




I am glad to see your example. It points exactly to the issue: EPR of 
WS-Addressing (WS-A) alone is not sufficient in MC case, and it is not 
sufficient for many other use cases as well, e.g. use case of your 
example, our delivery through proxy case, MC case, and many other use 
cases pointed by Asir in 
http://lists.w3.org/Archives/Public/public-ws-resource-access/2009Mar/0132.html 
. 
  
When looking at other potential WS-* standards for help, we should not 
overlook what has already been provided in WS-E specs, as well as many 
deployed WS-E applications and use cases that follow the WS-E specs to 
deal with the similar situation. 
  
In particular, the Mode attribute of Delivery in WS-E specs is for the 
subscriber to specify the additional critical requirements for event 
delivery. It is part of the WS-E semantics to critically support these 
applications. It is a simple and light weight solution without requiring 
other WS-* standards. It specifies: if event source does not support the 
requested event delivery as specified by the Mode attribute of Delivery, 
it should fault the event subscription with "
wse:DeliveryModeRequestedUnavailable fault indicating that the requested 
delivery mode is not supported". 
  
Thanks 
  
- Wu Chou. 
  
Wu Chou, IEEE Fellow, Ph.D. | Director |Avaya Labs Research | AVAYA | 233 
Mt. Airy Road| Rm. 2D48 | Basking Ridge, NJ 07920 | Voice/Fax: 
908-696-5198 / 908-696-5401 | wuchou@avaya.com 

From: Christopher B Ferris [mailto:chrisfer@us.ibm.com] 
Sent: Monday, April 13, 2009 4:13 PM
To: Chou, Wu (Wu)
Cc: Asir Vedamuthu; Li, Li (Li); public-ws-resource-access@w3.org; 
public-ws-resource-access-request@w3.org
Subject: RE: issue 6432 - yet another proposal

If the subscriber sent the following: 

<wse:Subscribe> 
           <wse:Delivery> 
                       <wse:NotifiyTo> 
                           <wsa:Address>ftp://example.org/sockittome/

</wsa:Address> 
                       </wse:NotifyTo> 
           </wse:Delivery> 
</wse:Subscribe> 

... and the Event source had no capacity for sending events via the FTP 
protocol, how would that be different than the MC case that you assert 
requires some special extensions to an endpoint that does not understand 
MC? 

If the subscriber required 2048bit encryption of the event content and 
WS-Security was not supported by the source, is that different? 

Of course not. Some means of achieving mutual compatibility of the 
requirements of the sink with the capabilities of the source is needed 
in order to enable effective composition of the various WS-* specs. 

The W3C WS-Policy WG spent the better part of 18 months producing the 
WS-Policy 1.5 Framework and Attachments Recommendations 
for just this use case - and lo and behold, WS-MC even defined a policy 
assertion vocabulary (as did WS-A and WS-Sec). Let's not 
pretend that none of that happened - after all, this is the same working 
group that is producing WS-MEX, which is designed to 
enable exchange of the policy and other metadata of an endpoint, is it 
not? 

Cheers,

Christopher Ferris
IBM Distinguished Engineer, CTO Industry Standards
IBM Software Group, Standards Strategy
email: chrisfer@us.ibm.com
blog: http://www.ibm.com/developerworks/blogs/page/chrisferris

phone: +1 508 234 2986 



From: 
"Chou, Wu (Wu)" <wuchou@avaya.com> 
To: 
"Asir Vedamuthu" <asirveda@microsoft.com> 
Cc: 
<public-ws-resource-access@w3.org>, "Li, Li (Li)" <lli5@avaya.com> 
Date: 
04/13/2009 02:27 PM 
Subject: 
RE: issue 6432 - yet another proposal 
Sent by: 
public-ws-resource-access-request@w3.org





It is a good idea to have a paper that explains how WS-MakeConnection (MC) 
composes with WS-Eventing and how it interworks with other WS-Addressing 
(WS-A)/WS-Eventing (WS-E) endpoints that do not support MC. We will also 
be interested to contribute to such a paper. 
 
One particular question is: WS-A 1.0 Core specifies: "Comparison of 
[destination] property values is out of scope, other than using simple 
string comparison to detect whether the value is anonymous, that is, where 
[destination] has the value http://www.w3.org/2005/08/addressing/anonymous

." 
From WS-A Core, it seems that some extension from WS-A implementation is 
needed in order to detect and understand the special MC anonymous EPR.  If 
such extension is beyond the mandatory features of a WS-A endpoint, it 
would make sense to specify it as out-of-band to avoid additional 
requirements on a regular WS-A endpoint implementation. 
 
The concern is: if the WS-A implementation cannot identify the special MC 
anonymous EPR by the simple string comparison as specified in WS-A 1.0 
Core, it might treat the the special MC EPR as a regular EPR, and accept 
the event subscription to send events  to it (MC anonymous EPR). If that 
happens, it could cause a major problem and the events  won't be able to 
deliver.   
 
To be concrete, assume there is an event source that understands WS-E and 
WS-A, but does not support MC. When the event subscriber sends a Subscribe 
message using the MC extension: 
<wse:Subscribe> 
           <wse:Delivery> 
                       <wse:NotifiyTo> 
                           <wsa:Address>http://docs.oasis-open.org/ws-718 
rx/wsmc/200702/anonymous?id=550e8400-e29b-11d4-a716-446655440000
</wsa:Address> 
                       </wse:NotifyTo> 
           </wse:Delivery> 
</wse:Subscribe> 
 
The event source checks the <wse:NotifyTo> EPR according to WS-A and 
decides it is neither “http://www.w3.org/2005/08/addressing/anonymous” nor 
“http://www.w3.org/2005/08/addressing/none” . Then it assumes it is an 
addressable EPR and will deliver notifications to it, which of course will 
fail. 
 
This means using EPR alone to indicate MC style delivery will put an event 
source in one of the two situations: 
1) The event source can be hit by a latent error because it does not 
recognize MC. 
2) To avoid the latent error, the event source has to recognize the MC 
extension, even though it does not support MC. 
 
- Wu Chou. 

From: Asir Vedamuthu 
Sent: Friday, April 10, 2009 5:00 PM
To: Christopher B Ferris
Cc: public-ws-resource-access@w3.org
Subject: RE: issue 6432 - yet another proposal 
 
> Any event sink would be foolish to engage in MC interchange with 
> an event source that did not advertise MC support in its policy. 
 
Using WS-MakeConnection policy assertion to indicate the use of 
WS-MakeConnection protocol is possible. Earlier in the same mail thread 
[1], we mentioned that tiny subscribers are resource-challenged and may 
not have access to or may not understand metadata. 
 
Anyway, such usages are outside the scope of WS-Eventing and should work 
with out-of-band agreements (and such agreements can be represented as a 
policy assertion). 
 
Having said that, the Working Group should consider authoring a paper that 
explains how WS-MakeConnection composes with WS-Eventing using Doug’s 
quoted sample as a starting point. We will be happy to help. 
 
[1] 
http://lists.w3.org/Archives/Public/public-ws-resource-access/2009Apr/0027.html 

 
Regards, 
 
Asir S Vedamuthu 
Microsoft Corporation 
 
From: Christopher B Ferris [mailto:chrisfer@us.ibm.com] 
Sent: Thursday, April 09, 2009 6:32 AM
To: Asir Vedamuthu
Cc: public-ws-resource-access@w3.org
Subject: RE: issue 6432 - yet another proposal 
 
Asir, 

It says that comparison of destination properties is out of scope. It does 
not say that it is disallowed. The reason that that 
statement is there is because URI comparison is non-trivial when you take 
into consideration all of the possible permutations 
of encodings that might be used. Many specs have deferred to 
straight-forward string comparison as a means of side-stepping 
the complexity. 

As for your implied assertion that _all_ implementations need to 
understand MC, that is ludicrous. No one has suggested that, nor is it 
necessary. Why do you think we spent all that time developing WS-Policy? 
MC has a policy assertion. Any event sink would be 
foolish to engage in MC interchange with an event source that did not 
advertise MC support in its policy. 

Cheers,

Christopher Ferris
IBM Distinguished Engineer, CTO Industry Standards
IBM Software Group, Standards Strategy
email: chrisfer@us.ibm.com
blog: http://www.ibm.com/developerworks/blogs/page/chrisferris

phone: +1 508 234 2986 

From: 
Asir Vedamuthu <asirveda@microsoft.com> 
To: 
Christopher B Ferris/Waltham/IBM@IBMUS, "public-ws-resource-access@w3.org" 
<public-ws-resource-access@w3.org> 
Date: 
04/08/2009 11:08 PM 
Subject: 
RE: issue 6432 - yet another proposal


 








A WS-Addressing-aware implementation or library is NOT required to run 
character by character comparison to infer that a WS-MakeConnection 
extension is required to speak with an Event Sink. 
“Comparison of [destination] property values is out of scope, other than 
using simple string comparison to detect whether the value is anonymous, 
that is, where [destination] has the value "
http://www.w3.org/2005/08/addressing/anonymous".” [1] 
An Endpoint Reference with encoded special semantics (WS-MakeConnection 
URI) ONLY makes sense IFF both sender and receiver understand the special 
semantics. This means, an Event Source (that is unaware of 
WS-MakeConnection) will not issue a fault that the Event Source does not 
understand the special semantics encoded in an Endpoint Reference. 
What is the justification to require all WS-Eventing implementations to 
recognize WS-MakeConnection URI? 
[1] 
http://www.w3.org/TR/2006/REC-ws-addr-core-20060509/#msgaddrpropsinfoset 
Regards, 

Asir S Vedamuthu 
Microsoft Corporation 

From: public-ws-resource-access-request@w3.org [
mailto:public-ws-resource-access-request@w3.org] On Behalf Of Christopher 
B Ferris
Sent: Wednesday, April 08, 2009 1:29 PM
To: public-ws-resource-access@w3.org
Subject: Re: issue 6432 - yet another proposal 

Jeff is correct. Opacity is not a quality of an URI. It is a principle: 
you should not infer anything from the 
structure (or the content) of the path component of the URI. Note the use 
of the word "should" - I'll come back to that 
later. 

For instance, just because an URI ends in .pdf does NOT mean that the 
client/agent that uses that URI in a GET 
should expect to receive an application/pdf media type in the response 
entity body. 

So, repeat after me, opacity is not a quality, it is a principle. One URI 
is neither more, nor less "opaque" than another. 
Period. 

Now, what Asir may be alluding to is that the MC Anon URI is constructed 
from a URI template: 

     http://docs.oasis-open.org/ws-rx/wsmc/200702/anonymous?id=

{unique-String} 

Here's where the opacity principle can be ignored: when the URI authority 
provides explicit information as to how to 
interpret the structure of the URI, as the WS-Make Connection spec [1] 
does. One can do a character for character 
match of the string 

     http://docs.oasis-open.org/ws-rx/wsmc/200702/anonymous?id= 

If it matches the first 58 characters of another URI, then that (other) 
URI is a MCanon URI. 

I refer you to the TAG finding that specifies that such practice is just 
fine thank-you very much [2] (3nd bullet in conclusions section): 

"* Assignment authorities may publish specifications detailing the 
structure and semantics of the URIs they assign. Other users of those URIs 
may use such specifications to infer information about resources 
identified by URI assigned by that authority." 

[1] 
http://docs.oasis-open.org/ws-rx/wsmc/200702/wsmc-1.1-spec-os.html#_Toc162743905 

[2] http://www.w3.org/2001/tag/doc/metaDataInURI-31-20061204.html 

Cheers,

Christopher Ferris
IBM Distinguished Engineer, CTO Industry Standards
IBM Software Group, Standards Strategy
email: chrisfer@us.ibm.com
blog: http://www.ibm.com/developerworks/blogs/page/chrisferris

phone: +1 508 234 2986 

From: 
Jeff Mischkinsky <jeff.mischkinsky@oracle.com> 
To: 
Yves Lafon <ylafon@w3.org> 
Cc: 
Gilbert Pilz <gilbert.pilz@oracle.com>, Asir Vedamuthu 
<asirveda@microsoft.com>, Doug Davis/Raleigh/IBM@IBMUS, 
"public-ws-resource-access@w3.org" <public-ws-resource-access@w3.org> 
Date: 
04/08/2009 03:16 PM 
Subject: 
Re: issue 6432 - yet another proposal 
Sent by: 
public-ws-resource-access-request@w3.org

 


 






hi,
My understanding of the use of "opaque" wrt to URI's is that you 
are not supposed to infer anything from the structure of the URI, not 
that specific uri's don't have specific "meanings"/semantics as 
defined in specs.
Otherwise it is totally meaningless to define a uri and give it 
semantics.
So this argument and asir's response don't make sense to me. You can 
certainly tell that the 2 uri's in question are different and you can 
certainly know what the semantics of using them are. So i don't see a 
problem.
-jeff
On Apr 08, 2009, at 2:34 AM, Yves Lafon wrote:

> On Tue, 7 Apr 2009, Gilbert Pilz wrote:
>
>> WS-Addressing 1.0 - Core defines two "special" URIs;
>> "http://www.w3.org/2005/08/addressing/anonymous" and
>> "http://www.w3.org/2005/08/addressing/none". Messages targeted to 
>> either
>> of these URIs are processed differently from messages targeted to
>> "normal" URIs such as "http://webserivce.bea.com/. . .".
>
> Well, they are different, but unless you know WS-Addressing, or 
> unless you resolve http://www.w3.org/2005/08/addressing/anonymous 
> and find out the relationship between this URI and the WS-Addressing 
> spec.
> If you resolve http://webservice.bea.com/... you will probably have 
> information about the endpoint, or you may know it in advance from 
> another document. So both URIs are opaque, unless you know their 
> semantic.
>
>
> -- 
> Baroula que barouleras, au tiéu toujou t'entourneras.
>
>        ~~Yves
>
>

--
Jeff Mischkinsky  jeff.mischkinsky@oracle.com
Director, Oracle Fusion Middleware  +1(650)506-1975
             and Web Services Standards                           500 
Oracle Parkway, M/S 2OP9
Oracle  Redwood Shores, CA 94065









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