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WS Orchestration

WS Orchestration. http://tmitwww.tm.tue.nl/staff/wvdaalst/Publications/p176.pdf. http://www-106.ibm.com/developerworks/webservices/library/ws-bpelcol2/. http://devresource.hp.com/drc/technical_white_papers/WSOrch/WSOrchestration.pdf. Eyal Oren DERI 2004/04/07. Survey of WS orchestration.

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WS Orchestration

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  1. WS Orchestration http://tmitwww.tm.tue.nl/staff/wvdaalst/Publications/p176.pdf http://www-106.ibm.com/developerworks/webservices/library/ws-bpelcol2/ http://devresource.hp.com/drc/technical_white_papers/WSOrch/WSOrchestration.pdf Eyal Oren DERI 2004/04/07

  2. Survey of WS orchestration • definitions & requirements • survey of standards • BPEL4WS • BPML • WSCI • survey of vendors

  3. Definitions this is the private process, our orchestration is subset of this • orchestration • executable process (that interacts with other web services) • control from the perspective of one business partner • for implementation • workflow • choreography • sequence of messages • public message exchanges • for collaboration • protocols this is like our choreography

  4. Requirements • a-synchronicity • need message correlation: identifying returning calls • exception management • services (operations) throw & catch exceptions • compensating transactions • resource locking not feasible • reusable composition: • separation process logic – used web services • don’t understand, looking for hierarchy? we need to have this we need to have this we need to have this goal – capability separationweb service – capability separation

  5. Standards overview • BPEL4WS • describes (control logic for) coordination of web services • Microsoft, IBM, BEA (XLANG & WSFL) • execution environment (BPWS4J) • not considered by W3C : not royalty-free • BPML • describes executable business processes • Intalio, Sun, …, bpmi.org/members.esp • WSCI • describes messages between collaborating web services • Sun, SAP, BEA, Intalio

  6. Standards relation

  7. BPEL4WS (1) • (control logic for) coordination of web services • abstract processes: • choreography • public message exchange • executable processes: • orchestration • private workflow • on top of WSDL

  8. BPEL4WS (2) • primitive activity (input & input-output operations) • invoke (an operation on a web service) • receive (waiting for invocation) • reply (responding, in input/output operation) • wait (for … time) • assign (copy & compute data to variables) • throw (exception) • terminate (stop service instance) • empty • structure activity (control flow) • combines primitives using: sequence, branch, loop, pick, flow • need more time to investigate possibilities

  9. BPEL4WS (3) (WSDL defines messages, operations, porttypes) • link • describes conversation between two roles • (specifies porttype of service, to receive messages) • multiple messages can be exchanged during conversition • partner: web service with role in linktype • business process: list of activities (with partners) • actual web service grounding can be dynamic • unclear yet (WS-Adressing) • BPWS4J uses hard-wired at deploy we need this too (as Axel said on wsmo-d)

  10. BPML • language for describing business processes • simple activity • action, assign, call, compensate, delay, fault, synch • complex activity • all, choice, foreach, sequence, switch, until, while • transaction support (compensation, nesting) • exception handling (throw, timeout)

  11. WSCI • language for describing web services collaboration • message correlation • sequencing rules • basic: call, delay, empty, fault, spawn, join • complex: all, choice, foreach, sequence, switch, until, while • but cannot specify input/output • exception handling • transactions is this really only public message exchange then?

  12. Comparison • BPEL4WS – BPML+WSCI • intentions are the same • no comparison in the article, no thorough search • vd Aalst: pattern-based comparison: • WSCI – BPML • offer same functionality • too much overlap to justify separation • WSCI can be used to model • BPEL4WS – BPML • little more expressive • no semantics • too many overlapping constructs

  13. Useful for WSMO • either: borrow requirements • asynchronicity • exception management • compensation • message correlation • control flow construct (workflow patterns, vd Aalst) • or: use a standard

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