Workflow programming

1
Workflow programming
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Graphical workflows

• As discussed, WS-BPEL is an XML-based language
  for workflow programming
• However, it is verbose and clumsy so more
  readable graphical languages have been developed
• BPMN (Business Process Modelling Notation) has
  been proposed as a standard graphical workflow
  language

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BPMN

• Key concepts
• Activities - things which are done as part of a
  workflow (rounded rectangle)
• Events - something which happens that causes a
  change in the workflow (circle)
• Gateways - a selection point (diamond)
• Sequence flow - Ordering relation. (solid arrow)
• Message flow - exchange of information (dashed
  arrow)
• Pool - a participant in a process (rectangle)

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Programming a workflow

• Think about activities and the end-to-end
  sequence to complete a process
• Think about the participants in the process -
  each should be in a separate pool
• Think about gateways (choices). What happens when
  an activity terminates abnormally.
• Think about what information is exchanged by the
  activities involved

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Hotel booking workflow
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Workflow example

• ADSL problem management in an ISP
• Workflow involves interactions between
• Customer and ISP
• ISP and Telecomms company
• Assume customer is having problems with their
  home broadband connection and is trying to get
  these fixed
• Draw a graphical workflow showing activities and
  interactions between the customer, the ISP and
  the telecomms companies

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Workflow information

• You have to think about the activities involved
  in the workflow and ask me about what goes on
• I will answer based on my recent experience of
  having a difficult problem fixed.