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Subject: RE: [wsbpel] Issue 11 - Creation of Repeating/Optional XML Structures
Danny, There is now doubt that today BPEL is crippled because it only supports very limited data manipulation (data initialization, array/looping, update). There is also no doubt that this is a slippery slope. One option might be to allow tighter integration between BPEL and XQuery (as suggested by Alex Yiu earlier in this forum). But even that integration work might be out of the scope of the initial delivery of the spec as this is something that can be layered on at a later point of time without impacting to our current work. Edwin -----Original Message----- From: Danny van der Rijn [mailto:dannyv@tibco.com] Sent: Tuesday, February 03, 2004 10:33 AM To: wsbpel@lists.oasis-open.org Subject: [wsbpel] Issue 11 - Creation of Repeating/Optional XML Structures At our September F2F, I presented some alternatives for addressing issue 11. The alternative were met with some opposition to even addressing the issue at all. In order to get the conversations going again, I'd like to present a very high level view of the pros and cons of addressing the issue. It seems most appropriate to me to begin at this level, before spending any more time actually trying to solve the issue. The issue: To modify a variable's XML structure, one uses the <assign> <from/> <to variable="ncname" part="ncname"? query="queryString"?/> </assign> syntax. "For XPath 1.0, the value of the query attribute MUST be an absolute locationPath (with '/' meaning the root of the document fragment representing the entire part). It is used to identify the root of a subtree within the document fragment representing the part. The location path MUST select exactly one node. If the location path selects zero nodes or more than one node during execution, then the standard fault bpws:selectionFailure MUST be thrown by a compliant implementation." What this ends up meaning is that if there is a repeating element that has N instances of the element, the N+1th may not be created. Additionally, if there is an optional element that is not present, it can not be created. Pro-Issue 11: There are many use cases where the creation of repeating and/or optional elements is required. A notable one is looping over an array of inputs, calling a service on each one, and creating an array of outputs. There are many more. BPEL would be crippled without this feature. Anti-Issue 11: BPEL has some very primitive data handling capabilities, but should never have full-blown data handling capabilities. If the language is modified to solve this problem, we are starting down a slippery slope. What will the next data handling addition be? When will the ocean be boiled? If data handling capabilites beyond what are currently included are needed, then simply call out to a data handling/modification service. 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/leave_workgroup. php.
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