Transactions != Business Processes William Cox, Ph.D. OASIS Symposium on Reliable Infrastructure New Orleans 26 April 2004

Cox OASIS Symposium a2 Outline Motivation and History Common Misconceptions Need for Transactions BPEL and WS-BA not equivalent Common Misconceptions (reprise) Summary References

Cox OASIS Symposium a3 Motivation Business Processes and [long-running distributed] Transactions have some similarities Misconceptions about their relationship –Both what that relationship is, and what it should/could be If transactions support business processes, and business processes can do transactions… Deeper look

Cox OASIS Symposium a4 History XA (X/Open) ACID Transactions OMG Object Transaction Service –And Extended Structures for OTS BTP (similar goals but more complex) BPEL4WS (BEA, IBM, MS 2002) WS Business Process Execution Language OASIS Technical Committee Our examples and sketches are based on recent versions of –BPEL4WS 1.1 [BPEL] –WS-BusinessActivity 1.1 [WS-BA] –WS-Coordination 1.1 [WS-C]

Cox OASIS Symposium a5 Long-running transactions Many Business Transaction Specs –Business Transaction Process (OASIS TC 2000, C Draft 2002) –WS-Transaction/WS-Coordination (BEA/IBM/Microsoft ) –WS-CAF (Sun/Oracle/Iona 2003, OASIS TC) Termination protocols, coordination protocols Consistent results of an activity

Cox OASIS Symposium a6 Outline Motivation and History Common Misconceptions Need for Transactions BPEL and WS-BA not equivalent Common Misconceptions (reprise) Summary References

Cox OASIS Symposium a7 Common Misconceptions Heard around the industry: –Since a transaction tree is similar to a business process graph, business processes can do transactions –If you have business processes you don’t need transactions –If you have business processes you ONLY need atomic transactions –WS-BusinessActivity requires WS-Coordination which requires a single coordinator, and that’s a problem for distributed systems –Transactions can be hidden completely within a business activity, so if you need them you can use anything you want (and mix and match) –If business processes need transactions, and transactions can be implemented by business processes, isn’t this an infinite recursion? –You don’t need transactions for business process failure recovery –Interoperation of transaction protocols isn’t needed

Cox OASIS Symposium a8 Need for Distributed Transactions Inter-enterprise error recovery –Too much recovery is manual, expensive, and slow A phone call can be expensive and not just in $$ –Don’t want a custom recovery algorithm for each pair of partners! –This is biggest economic benefit of distributed transactions Conciseness of expression –BPEL is a clumsy way to express transactional semantics

Cox OASIS Symposium a9 A Business Process Consider a lender who wants to create as part of a loan approval process a BP to get credit reports from three different credit bureaus then calculate a credit score

Cox OASIS Symposium a10 A Business Process (continued) Each Credit Bureau may have different –Logging –Recovery –Legal requirements” Which in turn forces the lender to deal with three different recovery mechanisms “… the absence of [a] well-defined protocol forces me to…over engineer error handling for every service and system as a whole.” - CNA Insurance to BTP- comment list, 2003

Cox OASIS Symposium a11 Outline Motivation and History Common Misconceptions Need for Transactions BPEL and WS-BA not equivalent Common Misconceptions (reprise) Summary References

Cox OASIS Symposium a12 WS-BA emulating BPEL? No WS-BA is a protocol, not an execution environment WS-BA doesn’t express BPEL constructs such as –Switch –While –Links –Message Properties –Expressions and assignment No separate notion of state in WS-BA

Cox OASIS Symposium a13 BPEL emulating WS-BA? Yes, but not quite: BPEL join conditions are clumsy for WS-BA semantics –No Boolean optimization; all branches must evaluate So use PICK –But PICK order of selection is implementation-defined Exponential state expansion to deal with incomplete branches –WS-BA user can program join conditions without limitations of BPEL

Cox OASIS Symposium a14 BPEL emulating WS-BA? (continued) BPEL expresses too much and too little –BPEL is a programming environment But hard to use vs Java, C#, etc Distributed agreement is not part of BPEL –Within a platform-specific implementation –BPEL recognizes need for WS-TX or equivalent

Cox OASIS Symposium a15 BPEL emulating WS-BA? (continued) BPEL a hard way to express common transactional situations BPEL is prescriptive on SOAP headers –Hard to layer without changes to the spec

Cox OASIS Symposium a16 Outline Motivation and History Common Misconceptions Need for Transactions BPEL and WS-BA not equivalent Common Misconceptions (reprise) Summary References

Cox OASIS Symposium a17 Common Misconceptions (reprise) Since a transaction tree is similar to a business process graph, business processes can do transactions –Similar doesn’t mean the same. BPEL can’t effectively do BA If you have business processes you don’t need transactions –You’ll need transactions for distributed agreement. Are you using web services for process steps? If you have business processes you ONLY need atomic transactions –Below the level of this talk. Atomic transactions aren’t distributed. WS-BusinessActivity requires WS-Coordination which requires a single coordinator, and that’s a problem for distributed systems –A non-issue. Who’s running your business process, by the way?

Cox OASIS Symposium a18 Common Misconceptions (reprise) Transactions can be hidden completely within a business activity, so if you need them you can use anything you want (and mix and match) –But if you care about recovery and need application logic you need to expose If business processes need transactions, and transactions can be implemented by business processes, isn’t this an infinite recursion? –No. You don’t want to use business processes to implement transactions, only to describe their semantics. You don’t need transactions for business process failure recovery –No you don’t. But you’ll save money and time by using transactions Interoperation of transaction protocols isn’t needed –Unless you have more than one business partner, and use more than one transaction protocol among your partners

Cox OASIS Symposium a19 Summary Recovery for multiple partnerships is hard. WS-BA can help WS-BA cannot express business processes as can BPEL BPEL can superficially describe BusinessActivity transactions, but cannot express their semantics in a meaningful and effective manner Don’t try to push application logic into transaction protocols. Use transaction protocols to support application logic Don’t believe everything you hear around the industry

Cox OASIS Symposium a20 References WS-Coordination WS-BusinessActivity IBM Links Alphabetization problems--some under “WS-”, some under “Web Services” Microsoft Links BEA Links Interoperability and Feedback WS Business Process Execution Language OASIS Technical Committee –