WS Orchestration

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WS Orchestration
http//tmitwww.tm.tue.nl/staff/wvdaalst/Publicatio
ns/p176.pdf
http//www-106.ibm.com/developerworks/webservices/
library/ws-bpelcol2/
http//devresource.hp.com/drc/technical_white_pape
rs/WSOrch/WSOrchestration.pdf

• Eyal Oren
• DERI
• 2004/04/07

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Survey of WS orchestration

• definitions requirements
• survey of standards
• BPEL4WS
• BPML
• WSCI
• survey of vendors

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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
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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
• dont 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
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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

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Standards relation
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BPEL4WS (1)

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

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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

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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)
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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)

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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?
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Comparison

• BPEL4WS BPMLWSCI
• 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

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Useful for WSMO

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