Web Service Composition workflow patterns in BPEL4WS

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Web Service Compositionworkflow patterns in
BPEL4WS
http//tmitwww.tm.tue.nl/research/patterns/downloa
d/wfs-pat-2002.pdfhttp//tmitwww.tm.tue.nl/resear
ch/patterns/download/bpel_er.pdfhttp//www.big.tu
wien.ac.at/research/publications/2003/0603.pdf

• Eyal Oren
• DERI
• 2004/06/02

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Overview

• Goal
• Workflow Patterns
• Supported by BPEL4WS
• YAWL Yet Another Workflow Language
• Relevance to WSMO

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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

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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)

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Workflow patterns

• workflow
• process (control flow)
• information (data)
• organization (resource)
• operation (implementation)
• integration
• gathered control-flow patterns(www.workflowpatter
  ns.com)
• its not expressivity, almost all Turing
  completeits about suitability, direct support
• how good (necessary) are the patterns?

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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 8,9
not 10
not 18
not 14,15
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Basic Patterns
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Advanced Patterns
A1 audit_applicationA2 process_applicationC
close_case
paper accepted if both reviews positive, author
notifiedif firstnegative, notify author
immediately
paper accepted if all 2 out of 3 positive, author
notifiedif 2negative, notify author immediately
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Structural Patterns
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State-based Patterns
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BPEL Summary

• BPEL supports a lot of patterns(compared to
  languages considered)
• positive
• expressive
• negative
• should be simplified (WSFL, XLANG overlap)
• should be formalized

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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

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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

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YAWL Examples
multi-merge
milestone
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Relevance to WSMO

• Orchestration is (or needs) a way to describe
  composite processes
• Orchestration shouldnt re-invent the wheel
• Orchestration should (partly) support patterns
• Orchestration should use either
• BPEL
• YAWL