1. Service-Oriented Computing: Semantics, Processes, Agents
August 2004
Chapter 13: Process Specifications
Service-Oriented Computing: Semantics, Processes, Agents – Munindar P. Singh and Michael N. Huhns, Wiley, 2005
© Singh & Huhns

2. Highlights of this Chapter
Service-Oriented Computing: Semantics, Processes, Agents
August 2004
Highlights of this Chapter
Processes
Describing Dynamics with UML
Workflows
Business Process Languages
BPEL4WS (WS-BPEL)
ebXML
RosettaNet
PSL: Process Specification Language
Chapter 13
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
© Singh & Huhns

3. Processes and Workflows
Chapter 13
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

4. A Process Is … [Abstractions]
Service-Oriented Computing: Semantics, Processes, Agents
August 2004
A Process Is … [Abstractions]
Orchestration: A partial order of actions (activity graph, script) under the control of a central conductor; akin to a workflow [Global view; central]
Workflow: narrower concept than process; emphasizes control and data flows from a central perspective; usually tool-specific and focused on human tasks
Choreography: An exchange of messages among participants; akin to a conversation as described by WSCL, WS-CDL, ebBP [Global view; distributed]
Collaboration: A joint set of activities among business partners [Local views; distributed]
Chapter 13
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
© Singh & Huhns

5. Telecommunications Order Processing
Older workflow tools support specialized (ad hoc) notations
Chapter 13
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

6. Describing Dynamics with UML
UML Activity Diagrams are practically identical to BPMN (Business Process Modeling Notation) and WS-BPEL (Business Process Execution Language)
Sequence: a transition from one activity to the next
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
Chapter 13
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

7. UML Activity Diagram Implementation of a vendor’s purchase process
Chapter 13
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 pattern?
How would you accommodate exceptions in each pattern?
Chapter 13
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

9. WS-BPEL Metamodel Chapter 13
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

10. Process as a Composite Web Service
Chapter 13
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=" 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"/>
<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>
Chapter 13
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
Chapter 13
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
Chapter 13
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

14. Design of an ebXML System
Chapter 13
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

15. Discover Partner Information and Negotiate
Chapter 13
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
Chapter 13
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

17. Business Service Interface
Interfaces with the legacy system to have it play a role in a specific protocol (e.g., vendor in 3A4)
Is aware of its own Collaborative Protocol Profile
Handles transactions based on all current agreements (CPAs)
Chapter 13
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
Chapter 13
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?
Chapter 13
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

20. Service-Oriented Computing: Semantics, Processes, Agents
August 2004
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)
Chapter 13
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
© Singh & Huhns