Web Service Composition

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Web Service Composition
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Agenda

• Web service composition
• Orchestration and Choreography
• Workflow
• JBPM
• Comparison of different workflows
• BPEL

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Problem

• Plan a trip
• Flight reservation
• Hotel reservation

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• Planning the trip
• Flight Reservation (web service 1)
• Hotel Reservation (web service 2)
• Need for web service composition

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Business Process Challenges

• A number of processes or agents concurrently and
  cooperatively tries to achieve some goals.
• Coordinate asynchronous communication between
  services.
• Correlate message exchange between parties.
• Implement parallel processing of activities.
• Manipulate/transform data between partner
  interactions
• Support long running business transaction
• Provide consistent exception handling

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Solution- Web Service Composition

• Composed web services are
• Individual components implemented at different
  places.
• Execute in different contexts.
• Need to communicate to yield better results.

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Industry Solution

• Web service Interface design using WSDL
• Interaction and message exchange between
  different web services using BPEL.

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Recent history of Business Process Standards
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Orchestration Choreography
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Orchestration Choreography

• Orchestration and Choreography describe two
  aspects of creating business processes from
  composite Web services.

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Orchestration Choreography

• Orchestration refers to an executable business
  process that may interact with both internal and
  external web services. For orchestration, the
  process is always controlled from the perspective
  of one of the business parties.
• Choreography is more collaborative in nature, in
  which each party involved in the process
  describes the part they play in the interaction.

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Sample Business Process Purchase Order
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From a Choreography Perspective
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From an Orchestration Perspective
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Orchestration Choreography

• orchestration
• Compose web services for business processes
• control from the perspective of one business
  partner
• Composition in the part of sense
• workflow
• Choreography
• Compose web services for business collaboration.
• sequence of messages
• public message exchanges
• Composition in the sequencing sense
• Peer-to-peer model
• protocols

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Orchestration Choreography
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Standards relation
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Work Flow

• Traditional workflow processes
• Tens to a few hundreds of tasks
• Selection is humanly manageable
• Web services processes
• Thousands of web services available potentially.
• Impossible to manually browse and select most
  suitable ones.

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WorkFlow

• The automation of a business process, in whole or
  part, during which documents, information or
  tasks are passed from one participant to another
  for action, according to a set of procedural
  rules.

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WFMS

• A software component that takes as an input a
  formal description of business processes and
  maintains the state of process executions,
  thereby delegating activities among people and
  applications.

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WFMCs reference model
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Process Languages
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Process vs Program

• Graphical
• Lengthy

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Workflows used in UGA

• WebWork web based WFMS developed in LSDIS
• OrbWork CORBA based WFMS developed in LSDIS
• Enhydra Enhydra XPDL based WfMS used in CCRC
• JBPM jPDL/BPEL based WfMS used in CCRC
• Taverna Taverna
• - XScufl based WfMS used in CCRC, Kissinger

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Web service composition

• Orchestration
• WS-BPEL(OASIS specification)
• Active BPEL
• Oracle Process Manager
• IBM Websphere
• Microsoft BizTalk Server
• Choreography
• -WS-CDL(W3C specification)
• Semantic Web Services/Automatic Composition
• METEOR-S, OWL-S

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JBPM
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Focus

• State Management
• Task Management
• Deployment Freedom

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Layered Modelling
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Comparison of Different Workflows
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WebWork METEORs Web-based Workflow
Management System..

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Few characteristics of WebWork

• WebWork supports the creation of flexible
  workflows that include both manual and automated
  tasks, transactional and non-transactional tasks
  by coordinating the overall execution of the
  tasks.
• WebWork is designed for heterogeneous distributed
  environments spanning multiple organizations.
• a. Client access is universal since all that
  is required is a graphical Web browser.
• b. On the server side where the CGI programs
• are run, WebWork supports the use of multiple
  Web servers.

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Few characteristics of WebWork

• WebWork is designed to interoperate with OrbWork,
  NeoWork.
• It can also communicate with a variety of DBMS.
• WebWork provides low overhead yet what we believe
  to be effective recovery mechanisms.
• WebWork supports rapid workflow application
  development in which all workflow oriented code
  is automatically generated.

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BPEL
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BPEL4WS

• BPEL4WS Business Process Execution Language for
  Web Services
• XML based language for description of Web service
  according to the specified business rule
  business workflows
• BPEL offers
• Definition of business protocols
• Fault handling and compensation

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Web Service Framework
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BPEL
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Standard building blocks of BPEL
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BPEL Syntax

• ltprocessgt
• lt! Definition and roles of process
  participants --gt
• ltpartner Linksgt ... lt/partnerLinksgt
• lt!- Data/state used within the process --gt
• ltvariablesgt ... lt/variablesgt
• lt!- Properties that enable conversations --gt
• ltcorrelationSetsgt ... lt/correlationSetsgt
• lt!- Exception handling --gt
• ltfaultHandlersgt ... lt/faultHandlersgt
• lt!- Error recovery undoing actions --gt
• ltcompensationHandlersgt ... lt/compensationHandlers
  gt
• lt!- Concurrent events with process itself --gt
• lteventHandlersgt ... lt/eventHandlersgt
• lt!- Business process flow --gt
• (activities)
• lt/processgt

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BPEL4WS Basic Activities
Do a blocking wait for a matching message to
arrive Send a message in reply to a message that
was received through a Receive Invoke a one-way
or request response operation on a
portType offered by a partner Update the values
of variables or partner links with new data