Chapter 13: Process Specifications

1. Chapter 13:Process Specifications Service-Oriented Computing: Semantics, Processes, Agents– Munindar P. Singh and Michael N. Huhns, Wiley, 2005

2. Highlights of this Chapter • Processes • Describing Dynamics with UML • Workflows • Business Process Languages • BPEL4WS (WS-BPEL) • ebXML • RosettaNet • PSL: Process Specification Language Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

3. Processes and Workflows Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

4. Process Abstractions Orchestration: A process is a partial order of actions (activity graph, script) under the control of a central conductor; akin to a workflow [Global; central] Choreography: A process is an exchange of messages among participants; akin to a conversation as described by WSCL, WS-CDL, ebBP [Global; distributed] Collaboration: A process is a joint set of activities among business partners [Local; distributed] Workflow: narrower concept than process; emphasizes control and data flows from a central perspective; usually tool-specific and focused on human tasks Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

5. Telecommunications Order Processing Older workflow tools support specialized (ad hoc) notations Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

6. Describing Dynamics with UML Practically identical to BPMN (Business Process Modeling Notation) and WS-BPEL (Business Process Execution Language) • Sequence: a transition from one activity to the next in time • Branch: a decision point among alternative flows of control • Merge: where two or more alternative flows of control rejoin • Fork: a splitting of a flow of control into two or more concurrent and independent flows of control • Join: a synchronization of two or more concurrently executing flows of control into one flow Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

7. UML Activity Diagram Implementation of a vendor’s purchase process Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

8. Flow Interoperability Patterns • Among others: • Chained • Nested • Synchronized • What guarantees would you obtain from each? • How would you accommodate exceptions in each? Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

9. WS-BPEL Metamodel Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

10. Process as a Composite Web Service Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

11. Stock Quote Service in WS-BPEL <process name="simple" targetNamespace="urn:stockQuoter" xmlns:tns="urn:stockQuoter" xmlns:sqp="http://tempuri.org/services/stockquote" xmlns=&BPEL;/> <containers> <container name="request" messageType="tns:request"/> <container name="response" messageType="tns:response"/> <container name="invocationRequest" messageType="sqp:GetQInput"/> <container name="invocationResponse" messageType="sqp:GetQOutput"/> </containers> <partners> <partner name="caller" serviceLinkType="tns:StockQuoteSLT"/> <partner name="provider" serviceLinkType="tns:StockQuoteSLT"/> </partners> <sequence name="sequence"> <receive name="receive" partner="caller" portType="tns:StockQuotePT" operation="wantQuote" container="request" createInstance="yes"/> <assign> <copy> <from container="request" part="symbol"/> <to container="invocationRequest" part="symbol"/> </copy> </assign> <invoke name="invoke" partner="provider" portType="sqp:StockQuotePT" operation="getQuote" inputContainer="invocationRequest" outputContainer="invocationResponse"/> <assign> <copy> <from container="invocationResponse" part="quote"/> <to container="response" part="quote"/> </copy> </assign> <reply name="reply" partner="caller" portType="tns:StockQuotePT" operation="wantQuote" container="response"/> </sequence> </process> Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

12. Electronic Business Extensible Markup Language (ebXML) • Established jointly by • UN-CEFACT (United Nations Centre for Trade Facilitation and Electronic Business) • OASIS (Organization for the Advancement of Structured Information Standards) • Provides specification languages for business processes, business messages to facilitate trading agreements • Motivations: • Global standard for companies of all sizes • Automate finding business partners Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

13. ebXML Vocabulary • Unified Modeling Methodology (UMM) • Specialized UML for Business Processes • Collaboration Protocol Profile (CPP) • Describes a business with respect to its roles in specified processes, the messages it exchanges, and the transport mechanism (e.g., HTTPS) • Collaborative Partner Agreement (CPA) • Intuitively, like an “intersection” of two CPPs • Technical agreement between two or more partners • May be legally binding Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

14. Design of an ebXML System Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

15. Discover Partner Information and Negotiate Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

16. 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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

17. 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) Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

18. RosettaNet PIP for Creating a Purchase Order: The Content for ebXML • PIP: Partner Interface Process; an interaction protocol • ebXML BPSS: language for specifying PIPs • Two-party protocols • Request-response only • No specification of the meanings of the messages exchanged Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

19. Exercise: Exception in a Process Recording student registration • Assume that each database management system supports two-phase commit for transactions • Task #2 checks that the student has completed the necessary prerequisites for all the courses for which the student is registering Consider a scenario where Tasks #3, #4, #5 succeed, but 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 process to prevent problems such as this from occurring? Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

20. Chapter 13 Summary • In virtually all serious applications of SOC, services are composed into processes • Current approaches for process modeling are based on workflow abstractions • WS-BPEL enables specification of processes • ebXML also considers the life cycle of processes • RosettaNet is an application of ebXML • Flows interact in various ways • Exceptions in flows can be handled via (extended) transactions or through application-specific means (where interesting patterns can arise) Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns