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Subject: Re: [wsbpel] Issue - 123 - Matching <reply> with <receive>


With the original proposal correlating a receive and reply consists of:

Step 1 - Put a messageID attribute on the receive with a unique value.
Step 2 - Put a messageID attribute on the reply with a unique value.

With the modified proposal correlation a receive and reply consists of:

Step 1 - Declare a messageExchanges element
Step 2 - Put in a messageExchange entry with a unique name and an 
optional pattern.
Step 3 - Put a messageExchange attribute on the receive with a unique value.
Step 4 - Put a messageExchange attribute on the reply with the unique value.
Step 5 - Check to make sure that the receive and reply are both children 
of the scope that contains their messageExchange declaration from step 2 
otherwise move the declaration to another location.
Step 6 - If the messageExchange declaration is declared in a 
messageExchange declared in a sub-scope then look through all the parent 
scopes to make sure there isn't a messageExchange name collision since I 
suspect the usual name scoping rules will apply.

If later on the programmer wants to move an existing receive or reply, 
ones that already have messageExchange attributes, they have to go back 
and check to see if the messageExchange declaration is still in scope 
and if not, then move the declaration. Even if it is in scope, they have 
to make sure there is no name collision. Very quickly programmers will 
learn to start their processes with a single scope that contains nothing 
but a messageExchanges element so they can declare all of their 
messageExchanges in one place and not have to worry about scoping.

I am also worried about the pattern attribute. It is redundant 
information. The MEP is already declared in the WSDL so I don't see much 
value to declaring it twice. Also, I don't see how the pattern attribute 
really helps us with WSDL 2.0. Could you please expand on that point?

		Yaron


Satish Thatte wrote:

> 
> 
> I agree that we should not restrict combinations of WSDL interface 
> characteristics with usage in BPEL - e.g., that one cannot have two 
> outstanding requests on the same partnerLink and operation if the 
> operation response signature happens to omit the properties needed for 
> the correlation set used to disambiguate the request.
> 
> I also think that the requirement to have distinct correlations for 
> multiple outstanding requests is actually and, especially in case we 
> allow the proposed "engine managed" correlation (issue 96), clearly 
> unworkable.
> 
> I therefore like the R1 variant proposed by Yuzo.  It has the following 
> additional virtues
> 
> 1.  It gives a clear scope to the reply, thus allowing an internal fault 
> if a reply does not occur "in time".  Better control and error 
> detection.  Thus, for instance, the MEP declaration for a request 
> received in an event handler would be implicitly associated with the 
> implicit scope for the corresponding instance of that handler, and 
> therefore must be replied to inside the handler.
> 
> 2.  It allows for future new MEPs that may be supported in WSDL 2.0.  
> Better future proofing.  This is what I took Yuzo's "pattern" attribute 
> to be for.
> 
> I do not understand the arguments about "overhead".  As Yuzo has said, 
> this MEP-ID is an optional attribute.  The simple cases of 
> request/response do not need it.  In any case the overhead would not be 
> in runtime performance.
> 
> Satish
>  
> -----Original Message-----
> From: Ugo Corda [mailto:UCorda@SeeBeyond.com]
> Sent: Tuesday, July 06, 2004 11:03 AM
> To: Eckenfels. Bernd; wsbpel@lists.oasis-open.org
> Subject: RE: [wsbpel] Issue - 123 - Matching <reply> with <receive>
> 
> +1.
> 
> We should not expect modifications of the WSDL interface of the process 
> for the exclusive benefit of the underlying implementation of the 
> process itself (BPEL, in our case, but it could be, for instance, a Java 
> module instead - the Java module might also want its own modifications, 
> which could just happen to be different than the ones expected by BPEL, 
> so that the whole thing would be a big mess).
> 
> Ugo
> 
>  > -----Original Message-----
>  > From: Eckenfels. Bernd [mailto:B.Eckenfels@seeburger.de]
>  > Sent: Tuesday, July 06, 2004 2:23 AM
>  > To: wsbpel@lists.oasis-open.org
>  > Subject: RE: [wsbpel] Issue - 123 - Matching <reply> with <receive>
>  >
>  >
>  > Hello Yuzo,
>  >
>  > I dont think it is ok to require a response to have
>  > correlation values, if the businenss case (i.e. sync service)
>  > does not. Because this will not allow a BPEL Engine to
>  > provide services according to existing WSDL interface
>  > descriptions. I think we agree here, that this is not really
>  > a good thing.
>  >
>  > Mit freundlichen Grüßen
>  > Bernd Eckenfels
>  > Chief Architect
>  > --
>  > SEEBURGER AG - Edisonstr.1 , D-75015 Bretten, Germany
>  > Fax: +49 (0)7252 96-2400 - Phone: +49 (0)7252 96-1256
>  > mailto:b.eckenfels@seeburger.de - http://www.seeburger.de
>  >
>  >
>  > -----Original Message-----
>  > From: Yuzo Fujishima [mailto:fujishima@bc.jp.nec.com]
>  > Sent: Monday, July 05, 2004 4:13 AM
>  > To: wsbpel@lists.oasis-open.org
>  > Subject: Re: [wsbpel] Issue - 123 - Matching <reply> with <receive>
>  >
>  >
>  > Assaf,
>  >
>  > Assaf Arkin wrote:
>  > > Yuzo Fujishima wrote:
>  > >
>  > >> (To: Asaaf
>  >          ===== Sorry for the misspell here.
>  >
>  > >> Please reply to this message because the previous one have not
>  > >> reached the wsbpel mailing list.)
>  > >>
>  > >> Do you think the message to be sent by <reply> must contain the
>  > >> message properties that match the specified correlation set(s)?
>  > >
>  > >
>  > >>
>  > >> If the answer is yes, we don't need any new mechanisms.
>  > >>
>  > >> My guess is that we want to say no, for example, to accommodate
>  > >> simple yes/no reply message. Then we need a new mechanism.
>  > >
>  > >
>  > > Are you talking about generic request/response, or the case
>  > where you
>  > > have two (or more) outstanding requests on the same
>  > > partnerLink/operation? The correlation set only affects the
>  > latter. So
>  >
>  > I am talking about the latter. My assumption is that we need
>  > to specify only as many correlation sets as necessary to
>  > disambiguate the receive-reply correspondence.
>  >
>  > > the simple case remains simple, and I would hate for it to
>  > become more
>  > > complicated, but I don't see a clear need for a referencing
>  > mechanism.
>  > > As for two outstanding on same partnerLink/operation, in
>  > all the use
>  > > cases I could imagine for doing this, I would use message
>  > properties in
>  > > the response.
>  >
>  > OK. I think I understand your position. Let me confirm it.
>  > Suppose two receives with the same partner link, port type,
>  > operation but different correlation sets are outstanding.
>  > Following your rule, then the messages to be sent by two
>  > reply's must contain the message properties that are
>  > referenced by the correlation sets used for disambiguation.
>  > Do I understand you correctly?
>  >
>  > Further suppose that the above two request-response are
>  > performed synchronously using two connections, for example,
>  > via plain SOAP invocation. I think this is a very common
>  > case. Then the client sides don't need any message properties
>  > for correlation, because the responses are sent back in the
>  > same connections as for requests. Do you think it is OK to
>  > request the reply messages contain message properties in this case?
>  >
>  > Yuzo Fujishima
>  > NEC Corporation
>  >
>  > To unsubscribe from this mailing list (and be removed from
>  > the roster of the OASIS TC), go to
>  > http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/le
> ave_workgroup.php.
> 
> 
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> 
> 
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> 


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