- From: Geoff Bullen <Geoff.Bullen@microsoft.com>
- Date: Mon, 13 Apr 2009 16:20:58 -0700
- To: Christopher B Ferris <chrisfer@us.ibm.com>, "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@w3.org>, "public-ws-resource-access-request@w3.org" <public-ws-resource-access-request@w3.org>
- Message-ID: <5AAAA6322448AA41840FC4563A30D6E8439E72D0B9@NA-EXMSG-C122.redmond.corp.microsoft>
Chris,
> 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?
Let’s just focus at the above issue for a moment.
In the original submission, Eventing defined PUSH mode, which defined functionality that specifically stated that the event source had to send one-way messages to the event sink. The default mode, as expressed in the Eventing spec, was PUSH mode. I hope we agree on that.
We believe a common definition for PULL mode (as inferred from the original submission) would be that the event sink would communicate to the event source, using a request/response message, in order to get (pull) the next event notification from the event source. This involves not only the concept of defining a two way message to accomplish this, but also involves significant new work by the event source to store events for future retrieval (with subsequent implementation details around retention time, etc). I hope we can agree on that.
In the current incarnation of the proposal for 6432, PUSH mode has been changed to EPR mode and the meaning of mode is now somewhat blurred. EPR mode could be PUSH or it could be PULL, depending on the EPR that is placed in NotifyTo. The original concept of the default mode for an event source has now changed from “always send a one way message” to be – look at NotifyTo to determine whether it is PUSH or PULL. Note that underlying all of this, there is still a concept of PUSH and PULL because even in the new proposal if the event source does not understand MC then it will still try to PUSH messages to the EPR in NotifyTo. So now we have two concepts, both called mode, both of which are states that the event source has to understand:
1. Do I look at the NotifyTo EPR to determine what to do? (the proposal calls this mode)
2. Do I send out one way messages, or do I wait till the event sink contacts me? (the proposal has no explicit name for this, maybe it’s an internal mode)
Both of these require code to implement (PULL mode requires substantial code on top of just supporting MC). In the current proposal, 1. is handled through the mode attribute, 2. is handled by parsing the EPR. I hope we can agree on that as well.
No matter which way you do things, the event source needs to keep the state of, and run very different code paths, based on if it is handling the PUSH or the PULL concept. The event source does not really need to keep the state of mode = EPR, as described in the proposal, past the point at which it has parsed to NotifyTo EPR. I hope we can agree on that as well.
So, my first point revolves around if we need both of these “mode” definitions. If the mode attribute simply had the values PUSH and PULL as in the submitted spec (rather than EPR), then the code would already understand the context of what should be in the NotifyTo EPR. If the right type of address is not in the EPR, then it can complain with a fault. The concept of an “EPR mode flag” is not required to achieve this and appears redundant.
My second point revolves around the question you ask that I quoted at the top of this email - why is one EPR (say one based on FTP) different from another (say one based on MC). My answer is that the intent is different. If the mode = PUSH then the EPR in the NotifyTo is an address I need to send one-way messages to. If mode = PULL then the EPR better be something (like MC) that I can use to make PULL mode happen. So what does this mean in reality?
a) Submitted Version: if the event source does not implement PULL mode, and receives a PULL mode attribute, it returns a fault. Current Proposal: If event source does not understand MC (which now sets the internal mode to PULL) then it can’t create a fault for it, assumes it’s a PUSH mode EPR and at some point tries to send one-way messages to it and silently fails.
b) Submitted Version: if mode = PUSH, the event source will try to interpret NotifyTo as an address and send messages to it. This is your FTP case above. Current Proposal: if mode = EPR and MC is not implemented, the same thing will happen. In this case you are right, there is no difference.
c) If client wants to PULL, Submitted Version: if mode = PULL and NotifyTo is not MC then a fault can be generated (fat fingers). Current Proposal: if mode = EPR and NotifyTo is not MC, then event source will set internal mode to PUSH and silently fail.
d) If client wants to PUSH, Submitted Version: if mode = PUSH and an MC is provided (and event source supports MC) then a fault can be generated. Current Proposal: if mode = EPR and MC is implemented, then the event source will set internal mode to PULL and silently fail.
There are clearly cases (a, c, d) where if we were to use a mode = PUSH/PULL (Submitted Version) concept the results in terms of error handling are certainly different and, we contend, much better than using mode = EPR (Current Proposal).
My third point revolves around extensibility. It is likely that any PULL mode implementation will require some extra elements inside the delivery element (maybe time to keep events on the queue or something like that). Using the Submitted Version method, any extensions that are placed inside the delivery element can be related to the intended mode of operation, based on the mode (PUSH and PULL) defined by the delivery element and the event source can interpret them in that context. Using the new method this is not true. For example, if I do not understand MC, but have extra elements inside of the delivery element, then these elements will be accidentally interpreted as PUSH mode extensions rather than PULL mode extensions as intended.
Basically we think that the value of mode should represent the functionality the event sink is expecting the event source to provide, not some esoteric concept associated with where the event source has to now look to find out what functionality the event sink really wants. Our proposal is, as it has always been, that there is no need to change the value of the mode attribute from being PUSH (and PULL) to EPR. There appears no good reason to do so, and we believe there are a number of technical reasons why the status quo is actually better and more concise. We are fine with MC being one potential implementation of PULL mode.
--Geoff
From: public-ws-resource-access-request@w3.org [mailto:public-ws-resource-access-request@w3.org] On Behalf Of Christopher B Ferris
Sent: Monday, April 13, 2009 1:13 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/..<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
Received on Monday, 13 April 2009 23:21:52 UTC