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Re: [WS-Addressing] issue concerning reliable One-Way MEP detection

From: <sylvain.marie@fr.schneider-electric.com>
Date: Thu, 4 Jun 2009 15:41:03 +0200
To: Doug Davis <dug@us.ibm.com>
Cc: antoine.mensch@odonata.fr, Bob Freund <bob.freund@hitachisoftware.com>, public-ws-addressing@w3.org, public-ws-addressing-request@w3.org
Message-ID: <OF6E2A504A.EB03D864-ONC12575CB.00499F26-C12575CB.004B2B77@schneider-electric.com>

> checking all of the mU headers seems akin to checking the service's
metadata for one-wayness.

Well although it makes sense, I do not fully agree with this. In my opinion
the headers relate to the non-fonctional aspect of the service (the
endpoint's policy, the processing pipe, some ws-* features...) ; while the
action relates to the business aspect (i.e. it represents the operation to
invoke in the end). In our implementation the core driver only knows the
non-fonctional and delegates everything related to the functional part to
higher layers. It would not be very elegant for the driver to ask a service
if such or such operation is one way, whereas all other MEP and
addressing-related stuff is automatically handled...

Best regards,


             Doug Davis                                                    
             04/06/2009 14:26          Bob Freund                          
                                       , Sylvain Marie/FR/Schneider@Europe 
                                       Re: [WS-Addressing] issue           
                                       concerning reliable One-Way MEP     

Maybe but the spec doesn't actually say that.
However, I think there's another thing that implementations would need to
worry about.  Even in a one-way message should the service be expected to
return mustUnderstand faults or soap version faults? While its not required
to, those sure are nice things to return if you can.  So in those cases I
would hope that an HTTP 202 wouldn't be automatically returned before these
two checks were done - and checking all of the mU headers seems akin to
checking the service's metadata for one-wayness.

STSM |  Standards Architect  |  IBM Software Group
(919) 254-6905  |  IBM 444-6905  |  dug@us.ibm.com
The more I'm around some people, the more I like my dog.

 Bob Freund                                                                
 Sent by:                                                               To 
 public-ws-addressing-request@w          sylvain.marie@fr.schneider-electr 
 3.org                                   ic.com                            
 06/04/2009 07:05 AM                     antoine.mensch@odonata.fr         
                                         Re: [WS-Addressing] issue         
                                         concerning reliable One-Way MEP   

I would have thought that a wsa:replyTo element containing the child
<wsa:Address> http://www.w3.org/2005/08/addressing/none</wsa:Address> could
be used to infer a one-way message.

On Jun 3, 2009, at 10:05 AM, sylvain.marie@fr.schneider-electric.com wrote:


I have been working for the fast few years on Devices Profile for Web
Services (DPWS) specification, and especially on an implementation (
https://forge.soa4d.org/). DPWS 1.0 was originally referring to WSA
member's submission, while DPWS 1.1 specification has now moved to
WS-Addressing 1.0.

WS-Addressing specifies how messages corresponding to different Message
Exchange Patterns (MEP) are sent. However it does not seem to specify a
reliable way to detect which MEP is actually in use. In particular the
One-Way MEP may not be detected reliably, which prevents devices to make
any optimisation (for example, send the empty HTTP response for SOAP/HTTP
binding). The only alternative is to inspect the actionUri and refer to a
service's WSDL in order to retrieve the appropriate MEP.

In DPWS implementations we think that the driver should be able to
implement the default processing chain without necessary knowing about the
web services deployed on top of it. We first thought about using the
absence of "replyTo" as a good indicator for a One-Way MEP but since
WS-Addressing 1.0 this does not work any more, as replyTo always have a
default value ("anonymous"). No we are thinking about using the absence of
"messageId" as a clue to detectt One-Way MEPs but this is clearly a hack
and not something we may rely on in he future.

What is the opinion of WS-Addressing's WG about this ? Thank you very much
in advance,

Best regards,


 <0F385492.jpg>           Sylvain MARIÉ                                    
                          Embedded Software Engineer                       
                          +33 (0)4 76 57 67 31 / 34 67 31                  

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Received on Thursday, 4 June 2009 13:42:28 UTC

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