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Subject: RE: [wsbpel] Issue - 280 - discussion
The part of the rules that I'm questioning has to do with rule #2 and #5 which cover the single element part WSDL message. Do you read this to say that the QName for the element comes from the actual element data or the declaration of the <part element="qname"/> in the WSDL? There are cases where the QNames could be different. It would be possible to construct a WSDL message variable and populate it with an element for use with a <throw> that differed from the element QName in the part description. Perhaps the element used was part of a substitutionGroup or perhaps it was simply user error. In either case, I'd like to clarify which QName to use for the element when matching.
Here's rule #2 with my emphasis:
2. Otherwise if the fault data is a WSDL message type where the message contains a single part defined by an element and there exists a <catch> construct with a matching faultName value that has a faultVariable whose associated faultElement’s QName matches the QName of the element used to define the part then the fault is passed to the identified <catch> construct with the faultVariable initialized to the value in the single part’s element.
It seems to me that we're driving this match based on the <part element="qname"/> from the WSDL and not from the element data. If this is the intent, then it feels a little inconsistent since in the other cases we're basing the match on the contents of the data as opposed to some declaration of its type. If this is not the intent, then perhaps this section could do with a slight rewording to make it more clear?
From: Alex Yiu [mailto:firstname.lastname@example.org]
Sent: Monday, May 29, 2006 9:35 PM
To: Mark Ford
Cc: 'Dieter Koenig1'; 'Thomas Schulze'; email@example.com; Alex Yiu
Subject: Re: [wsbpel] Issue - 280 - discussion
Hope you had a good long weekend ... :-)
I would like to address your question about "ambiguities" of the last part of email.
The current rule is clear to me that we are doing an exact QName match. That is, substitutionGroup is not considered in the <catch> matching logic.
Further elaboration: <catch faultElement="foo:bar"> will catch only faults that is of either element whose exact QName is "foo:bar" or message type of single part of element whose exact QName is "foo:bar". And, it will NOT catch a fault of element "foo:bar2" which is a part of substitutionGroup of "foo:bar".
Our current <catch> rule does not touch any XML schema typing issue at all. If in future we are ready to handle XML schema typing in our <cach> matching rules, we can for sure consider adding support for substitutionGroup at <catch> with a switch (that is a 20% usecase).
Back to commenting a bit more on Dieter's proposal: if we had introduced "faultType", that I would consider it is a 50%~80% of people would expect type-matching, instead of QName matching. That was also what I mentioned to Yaron back in Fall 2005. Yaron decided not to deal with the type matching problem by not introducing the "faultType" attribute in NY F2F (Dec 2005).
Mark Ford wrote:
Does your proposal extend to elements as well? Specifically, should the declared type of the element variable be considered as opposed to its actual content? I'm not sure if others have interpreted the rules as I have but my reading is that the Qname of the element content drives the match except in the case of a single part WSDL message which relies on the declared type. Regardless of this issue is resolved, I think we should clarify the fault matching rules to remove an possible ambiguities. For example, what would happen if I had a schema that used substitutionGroups and threw a fault with an element within the substitutionGroup? Would the fault matching be driven by the declared type which was the head of the group or by the actual data which was one of the allowed substitutions? -----Original Message----- From: Dieter Koenig1 [mailto:firstname.lastname@example.org] Sent: Monday, May 29, 2006 10:00 AM To: email@example.com; Mark Ford Cc: Thomas Schulze; firstname.lastname@example.org Subject: Re: [wsbpel] Issue - 280 - discussion Hi Alex and Mark, rules 1 and 4 should take care of both element and type by means of strict QName matching. In other words, - when a variable is defined with a type ns:t then it can be caught using a faultType that specifies the same QName ns:t - when a variable is defined with an element ns:e then it can be caught using a faultElement that specifies the same QName ns:e This clarification would need to be added to the two rules, and the faultType attribute be added to catch. Kind Regards DK Dieter König Mail: email@example.com IBM Deutschland Entwicklung GmbH Senior Technical Staff Member Tel (office): (+49) 7031-16-3426 Schönaicher Strasse 220 Architect, Business Process Choreographer Fax (office): (+49) 7031-16-4890 71032 Böblingen Member, Technical Expert Council Tel (home office): (+49) 7032-201464 Germany Alex Yiu <alex.yiu@oracle. com> To Mark Ford 24.05.2006 19:47 <firstname.lastname@example.org> cc Thomas Schulze/Germany/IBM@IBMDE, email@example.com, Alex Yiu <firstname.lastname@example.org> Subject Re: [wsbpel] Issue - 280 - discussion Hi, [ Changing the subject line ... such the issue list can "correlate" this email thread ;-) ] Currently, there is a set of rules stated in section "12.5 Fault Handlers" to determine which <catch> will be used during fault handling. (under "in the case of faults thrown with associated date ...") As Mark stated, if we want to support XSD-type (both simple and complex type) in the <catch> clause, we need to modify that set of rules significantly. There are 6 rules involved in that set. They are just using element's QName matching and message type's QName matching there. The passed resolution intentionally avoid any type inheritance-based checking there. If we allow simple-type or complex-type based <catch> clause, it would be odd to some users, if we don't do any type inheritance-based checking (similar to Java catch). If we do inheritance-based checking (e.g. a "foo:AddressType" based <catch> can handle a "foo:USAddressType" fault), we would wander in the territory of "best-match" schema type semantics, which I am not sure any other spec has done that before. If we don't do inheritance-based checking, it may not be that simple either to resolve all the most appropriate <catch> either. e.g. which one will be matched? <catch faultType="foo:AddressType"> vs <catch faultElement="foo:AddressElem"> (where "foo:AddressElem" is based on "foo:AddressType") vs <catch faultMessageType="foo:AddressMsgType"> (where "foo:AddressMsgType" has a single part based on "foo:AddressType") I am quite sure if we spend enough time, there will be a matching algorithm developed. But, at the same time, the 80-20 rules applies here. That is, we may need to double the size of rules (from 6 to 12) for a 20% usecase? Complexity kills usability. Last, it may be too late for this cycle of spec to add such a new feature to <catch>. I hope my train of thoughts sound reasonable to you guys. Thanks! Regards, Alex Yiu Mark Ford wrote:I think this issue boils down to how we determine the type of the fault data. The current matching rules match element data by their QNames. There is a subtle difference with WSDL Message fault data that define a single part of type element. In this case, the QName for the fault data comesfromthe part's element type declaration as opposed to the actual data for that part. If we add support for type-typed variables, then we need to change how the type of the fault data is determined. The existing rules for determiningthetype of the fault data are insufficient in this regard because they look only at the element data itself which could be ambiguous with complextypesand elements. How do you propose to determine the type of the fault data? -----Original Message----- From: Thomas Schulze [mailto:ThomasSchulze@de.ibm.com] Sent: Tuesday, May 23, 2006 1:32 PM To: email@example.com Subject: [wsbpel] BPEL Issue 280 BPEL Issue 280 addresses an inconsistency between BPEL's <throw> and <catch>. While <catch> can only handle message-typed and element-typeddata,<throw> can additionally throw type-typed data. The proposal is to put the restriction on <throw> to be able to throw only message-typed and element-typed data. Before doing this, I would like to discuss the other opportunity, allowing <catch> to catch type-typed data. Rationale: The BPEL 2.0 spec builds on WSDL 1.1 which allows to have messages with multiple parts. These parts can either be element-typed or type-typed. For instance, assume the following WSDL message (from the initial example in section 5.1): <wsdl:message name="POMessage"> <wsdl:part name="customerInfo" type="sns:customerInfoType"/> <wsdl:part name="purchaseOrder" type="sns:purchaseOrderType"/> </wsdl:message> Besides i.e. receiving such a message in a message-typed variable, you can use <fromPart>. This means, you can receive this message in two type-typed variables: <bpel:variable name="CustomerInfo" type="sns:customerInfoType"/> <bpel:variable name="PurchaseOrder" type="sns:purchaseOrderType"/> <bpel:receive name="ReceivePOMessage" partnerLink="..." operation="..."> <bpel:fromPart part="customerInfo" toVariable="CustomerInfo"/> <bpel:fromPart part="purchaseOrder" toVariable="PurchaseOrder"/> </bpel:receive> Now imagine a process which makes use of only such type-typed variables. They never can be thrown when resolving the issue as proposed. If amodelerof a BPEL process needs to throw such a variable, he is forced tointroducea new message or element making use of that type and then throw this message-typed or element-typed variable. This problem have already been discussed in Issue 93 (http://www.choreology.com/external/WS_BPEL_issues_list.html#Issue93). The reasoning for not allowing to catch type-typed data was: "Throwing complex types as faults is vaguely odd and WS-I requires that all SOAP faults be defined using elements so in general Web Services faults are typically elements anyway." I think WS-I does not apply here, because <throw> and <catch> are BPEL internal constructs. If a BPEL process should produce a Web Service fault <reply> have to be used. BPEL does not put any restrictions on replying a fault. So why on throwing a fault? Additionally remember chapter 8.1: "The infoset for a complex typevariableconsists of a DII that contains exactly one child, which is an EII referenced by the document element property. ... However the children ofthedocument element MUST exclusively consist of the complex type values assigned to the variable." Does that mean that type-typed variables have to be internally represented as element-typed? (maybe one of the DII / EII / AII / TII experts cananswerthat question) If yes, the catch logic shouldn't differ that much from the existing when allowing to catch type-typed data. I appreciate any comments/further thoughts on this. Tanks in advance! Best regards/Mit freundlichen Grüßen, Thomas Schulze --------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that generates this mail. You may a link to this group and all your TCs inOASISat: https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php --------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that generates this mail. You may a link to this group and all your TCs inOASIS--------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that generates this mail. 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