Chapter 13: Process Specifications

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• Chapter 13Process Specifications

Service-Oriented Computing Semantics, Processes,
Agents Munindar P. Singh and Michael N. Huhns,
Wiley, 2005
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Highlights of this Chapter

• Processes
• Describing Dynamics with UML
• Workflows
• Business Process Languages
• BPEL4WS
• BPML
• ebXML
• RosettaNet
• PSL Process Specification Language

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Processes and Workflows
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Process Abstractions

• Orchestration views a process as a partial order
  of actions under the control of a central
  conductor akin to a workflow
• Choreography views a process as an exchange of
  messages among participants akin to a
  conversation as described by WSCL and WSCI
• Collaboration views a process as a joint set of
  activities among business partners
• Workflow a narrower concept than a process,
  which emphasizes control flows and data flows
  from a central perspective

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Describing Dynamics with UML

• UML provides graphical constructs that can be
  used to describe (1) actions and activities, and
  (2) their temporal precedences and flows of
  control. The allowable control constructs are
• Sequence, which is a transition from one activity
  to the next in time
• Branch, which is a decision point among
  alternative flows of control
• Merge, where two or more alternative flows of
  control rejoin
• Fork, which is a splitting of a flow of control
  into two or more concurrent and independent flows
  of control
• Join, which is a synchronization of two or more
  concurrently executing flows of control into one
  flow

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UML Activity Diagram
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Example Workflow for Telecommunications Order
Processing
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Workflow Interoperability Patterns
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BPEL4WS Metamodel
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A BPEL4WS process is a composite Web service with
a WSDL description
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Example BPEL4WS Specification for Stock Quotation
Composite Service

• ltprocess name"simple" targetNamespace"urnstockQ
  uoter" xmlnstns"urnstockQuoter"
  xmlnssqp"http//tempuri.org/services/stockquote"
  xmlnsBPEL/gt
• ltcontainersgt
• ltcontainer name"request" messageType"tnsreq
  uest"/gt
• ltcontainer name"response" messageType"tnsre
  sponse"/gt
• ltcontainer name"invocationRequest"
  messageType"sqpGetQInput"/gt
• ltcontainer name"invocationResponse"
  messageType"sqpGetQOutput"/gt
• lt/containersgt
• ltpartnersgt
• ltpartner name"caller" serviceLinkType"tnsSt
  ockQuoteSLT"/gt
• ltpartner name"provider" serviceLinkType"tns
  StockQuoteSLT"/gt
• lt/partnersgt
• ltsequence name"sequence"gt
• ltreceive name"receive" partner"caller"
  portType"tnsStockQuotePT"
• operation"wantQuote"
  container"request" createInstance"yes"/gt
• ltassigngt ltcopygt
• ltfrom container"request"
  part"symbol"/gt
• ltto container"invocationRequest"
  part"symbol"/gt
• lt/copygt lt/assigngt

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Electronic Business Extensible Markup Language
(ebXML)

• Established by UN-CEFACT (United Nations Centre
  for Trade Facilitation and Electronic Business)
  and OASIS (Organization for the Advancement of
  Structured Information Standards)
• Provides specifications to define standard
  business processes, exchange business messages
  and enter into trading agreements
• Motivations
• Global standard for companies of all sizes
• Automate finding business partners

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ebXML Vocabulary

• Unified Modeling Methodology (UMM)
• Specialized UML for Business Processes
• Collaboration Protocol Profile (CPP)
• Describes a businesss profile, i.e., which
  business processes it supports, its roles in
  those processes, the messages exchanged, and the
  transport mechanism for the messages (e.g.,
  HTTPS)
• Collaborative Partner Agreement (CPA)
• An intersection of two CPPs
• Technical agreement between two or more partners
• May be legally binding

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Design of an ebXML System
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Discover Partner Information and Negotiate
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Implementing ebXML

• ebXML is a set of specifications of
  collaborations and repositories for discovering
  business partners
• Build and deploy its custom ebXML-compliant
  application to implement necessary roles in
  different collaborations
• Use COTS ebXML compliant applications and
  components (from ERP vendors)
• Business Service Interface (BSI) a wrapper that
  enables a given party to participate properly in
  an ebXML exchange

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Business Service Interface

• Interfaces with the legacy system, e.g., to make
  it vendor in a specific protocol such as 3A4
• Is aware of its own Collaborative Protocol
  Profile
• Handles transactions based on all the current
  agreements (CPAs)

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RosettaNet PIP for Creating a Purchase Order The
Content for ebXML
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Exercise Exceptions in Workflows

• This workflow is for recording student
  registration. Assume that each database
  management system can implement the 2PC protocol
  for transactions. When a student registers, Task
  2 is a check with the Graduate Coordinator to
  verify that he has completed the necessary
  prerequisites for the courses for which he is
  registering. Assume that Tasks 3, 4, and 5
  succeed, but that Task 2 fails.
• As the system administrator, what operations
  would you have to perform in order to restore
  consistency to your system?
• How would you modify the workflow in order to
  prevent problems such as this from occurring in
  the future?

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Chapter 13 Summary