1. Web Service Composition workflow patterns in BPEL4WS Eyal Oren DERI 2004/06/02 http://tmitwww.tm.tue.nl/research/patterns/download/wfs-pat-2002.pdf http://tmitwww.tm.tue.nl/research/patterns/download/bpel_er.pdf http://www.big.tuwien.ac.at/research/publications/2003/0603.pdf

2. Eyal Oren2 Overview Goal Workflow Patterns Supported by BPEL4WS YAWL: Yet Another Workflow Language Relevance to WSMO

3. Eyal Oren3 Goal To analyse web service composition languages, specifically BPEL4WS Focus on control flow Learn from workflow management research “industry ignores established formal process modeling techniques: ignore the industry”

4. Eyal Oren4 Bernauer et. al. – Comparison Framework comparing interorganizational workflow different than intra-organizational workflow: –interoperability –autonomy (of participating organizations) –trust, privacy and security requirements: –re-usable workflow types (private/public, roles) –profile specifications (organization, role, technology) –implementation details (executable specification)

5. Eyal Oren5 Workflow patterns workflow: process (control flow) information (data) organization (resource) operation (implementation) integration gathered control-flow patterns (www.workflowpatterns.com) it’s not expressivity, almost all Turing complete it’s about suitability, direct support –how good (necessary) are the patterns?

6. Eyal Oren6 Patterns often-used patterns but often no direct support: providing solutions in ‘simpler’ language can also be used to analyse language usability (you would like direct support) not 10 not 18 not 8,9 not 14,15

7. Eyal Oren7 Basic Patterns sequence parallel splitflow (XLANG-style) or link (WSFL-style) synchronization (wait for all) flow/link exclusive choiceswitch/link (if you want OR: no switch) simple merge (one active branch) switch/link

8. Eyal Oren8 Advanced Patterns multi-choice sync. merge (one or more) link multi-merge (one or more) C as often as A1/A2 no support discriminatorno support (join only evaluated after all links determined) n-of-m joinno support A1 = audit_application A2 = process_application C = close_case paper accepted if both reviews positive, author notified if first=negative, notify author immediately paper accepted if all 2 out of 3 positive, author notified if 2=negative, notify author immediately

9. Eyal Oren9 Structural Patterns arbitrary cycles loops nested, ‘goto’ no support implicit terminationby default multiple instances nr. known design time flow, multiplying the number of instance invocations (hard code) run time before initiation no support run time, duringno support

10. Eyal Oren10 State-based Patterns deferred choice choose transportation based on then-available pick, based on messages interleaved par. routing end-of-year: add-interest, charge yearly cost in any order, but not at same time serializable scopes (semantics unclear, depends on transaction engine) milestone cancel order, if order placed, but only as long as not shipped no support cancel activity/caseterminate

11. Eyal Oren11 BPEL Summary BPEL supports a lot of patterns (compared to languages considered) positive: –expressive negative: –should be simplified (WSFL, XLANG overlap) –should be formalized

12. Eyal Oren12 YAWL Petri nets for workflow modeling: –formal semantics, yet graphical –state-based (not just event-based) –analysis techniques Problems: –(keeping track of) multiple instances –advanced synchronization patterns (either AND or XOR, depending on context) –cancellation pattern (vacuum cleaner) you can model everything, it just becomes unreadable and unmaintainable

13. Eyal Oren13 YAWL Petri-net based language Directly supports all patterns Formal semantics Control flow, data flow, operational perspective Supports web services Prototype software Future: –transactions, communication patterns –analysis techniques/tools

14. Eyal Oren14 YAWL Examples milestone multi-merge

15. Eyal Oren15 Relevance to WSMO Orchestration is (or needs) a way to describe composite processes Orchestration shouldn’t re-invent the wheel Orchestration should (partly) support patterns Orchestration should use either –BPEL –YAWL