1. CS 493/693: Distributed Systems Programming
V. “Juggy” Jagannathan
CSEE, West Virginia University
March 28, 2005

2. Chapter 7: Service Coordination Protocols
Web Services: Concepts, Architectures and Applications
G. Alonso et. al.
Springer Verlag

3. Next class: WS-Coordination WS-Transaction RosettaNet ebXML
End of today’s lecture
Next class:
WS-Coordination
WS-Transaction
RosettaNet
ebXML

4. WS-coordination Goals
A framework for supporting coordination protocols
A meta-specification
Supports mechanisms for communicating:
unique identifiers – using a structure called “coordination context”
the ports used in web services for participating in various conversations
the role that a participant plays in a given conversation using “action” interface

5. Components of WS-coordination

6. Centralized and distributed Coordination
Web service
Web service
Web service
coordinator
(a) central coordination
Web service
Web service
Web service
coordinator
coordinator
coordinator
(b) distributed coordination
Copyright Springer Verlag Berlin Heidelberg 2004

7. Components of WS-Coordination
Abstractions used
Coordination protocol – a set of rules governing conversations
Coordination type – grouping of coordination protocols
Coordination context – data structure that tracks instance identifier and pertinent information related to a conversation
Interaction forms
Activation – participant initiates a new context and creates a new conversation
Registration – a web service registers as a participant in a conversation
Protocol-specific interactions – messages exchanged in the context of executing a particular conversation

8. Activation of a new context in WS-coordination
ActivationRequestorPortType
Web service
CreateCoordinationContext
- ...
- coordination type
- current context
CreateCoordinationContextResponse
- ...
- coordination context
- identifier
- coordination type
- registration service
ActivationCoordinatorPortType
coordinator
Copyright Springer Verlag Berlin Heidelberg 2004

9. Registration in WS-Coordination
RegistrationRequestorPortType
Web service
register
- ...
- protocol identifier
- participant protocol service
registerResponse
- ...
- coordinator protocol service
RegistrationCoordinatorPortType
coordinator
Copyright Springer Verlag Berlin Heidelberg 2004

10. Convention for defining protocol-specific interfaces
XParticipantPortType
Web service
protocol-specific messages from participant to coordinator
protocol-specific messages from coordinator to participant
XCoordinatorPortType
coordinator
Copyright Springer Verlag Berlin Heidelberg 2004

11. Central Coordination

12. Types of messages exchanged
Operational messages – e.g. OrderGoods, RequestQuote
WS-coordination messages – e.g. activation, registration
Protocol-specific messages – to mark the start and end of various actions/activities associated with any conversation
WS-Coordination only provides standardization to WS-coordination type messages.

13. Sample types of messages exchanged
coordinator C
activation coordinator
registration coordinator
protocol coordinator
Web service A
Web service B
activation participant
protocol participant
activation participant
protocol participant
registration participant
Web service implementation
Web service implementation
registration participant
1. create CC
2. X1
3. register
4. protocol coordinator
5. operational message
6. register
7. protocol coordinator
8. protocol-specific message
9. protocol-specific message
Copyright Springer Verlag Berlin Heidelberg 2004

14. Distributed Coordination

15. Messages for distributed coordination
Web service A
coordinator Ca
Web service B
coordinator Cb
1. create CC
2. X1
3. register
4. protocol coordinator
5. operational message
6. create CC
7. X2
8. register
9. register
10. protocol coordinator
11. protocol coordinator
12. protocol message
13. protocol message
14. protocol message
15. protocol message
Copyright Springer Verlag Berlin Heidelberg 2004

16. Coordinator chaining for distributed coordination
XParticipantPortType
Web service n + 1
XParticipantPortType
XParticipantPortType
coordinator n
coordinator n + 1
XCoordinatorPortType
XCoordinatorPortType
Copyright Springer Verlag Berlin Heidelberg 2004

17. WS-Coordination summary
WS-coordination defines:
SOAP extensions for supporting coordination
Meta-protocols for creating coordination contexts, binding participants to coordinators
Mechanisms to support both central and distributed coordination
Mechanisms defined are similar to the ones defined by CORBA Object Transaction Service (OTS).

18. WS-Transaction

19. WS-Transaction Builds on top of WS-Coordination
Initially proposed by IBM, Microsoft & BEA in August 2002
Transactions in web services
Will have to deal with lack of a homogeneous middleware
Transactions likely to be long-running
Not always possible to impose ACID properties
Concepts which are precise in database operations may have no relevance in web services
Approach used in web services to deal with transactions
Notion of “compensation” as a way of rolling back “business activities”
Short duration transactions are handled similar to middleware and are called “atomic transactions”

20. Port types used in atomic transactions
WS-Coordination interfaces
ActivationCoordinatorPortType
RegistrationCoordinatorPortType
WS-Transaction interfaces
CompletionParticipantPortType
CompletionCoordinatorPortType
CompletionWithAckParticipantrPortType
CompletionWithAckCoordinatorPortType
atomic transaction coordinator
PhaseZeroParticipantrPortType
PhaseZeroCoordinatorPortType
2PCParticipantPortType
2PCCoordinatorPortType
OutcomeNptificationParticipantPortType
OutcomeNptificationCoordinatorPortType
WS-Transaction interfaces needed for chaining
RegistrationParticipantPortType
WS-Coordination interfaces
needed for chaining
Copyright Springer Verlag Berlin Heidelberg 2004

21. Example of atomic transaction in distributed coordination
Web service A
coordinator Ca
Web service B
coordinator Cb
create CC T1
register for Completion
completion coordinator
operational message T2
register for PhaseZero
PhaseZero coordinator
complete
PhaseZero
register for 2PC
2PC coordinator
PhaseZeroComplete
prepare
prepared
commit
committed
completed
Copyright Springer Verlag Berlin Heidelberg 2004

22. Port types used in “business activities” (long running transactions)
WS-Coordination interfaces
ActivationCoordinatorPortType
RegistrationCoordinatorPortType
WS-Transaction interfaces
BusinessAgreementParticipantPortType
BusinessAgreementCoordinatorPortType
BusinessAgreementWithCompleteCoordinatorPortType
BusinessAgreementWithCompleteParticipantrPortType
business activity coordinator
WS-Transaction interfaces needed for chaining
RegistrationParticipantPortType
WS-Coordination interfaces
needed for chaining
Copyright Springer Verlag Berlin Heidelberg 2004

23. An execution of the business activity protocol
Web service A
Web service B
Web service C
Coordinator R
create CC A1
operational message
operational message
register for BusinessAgreement
BusinessAgreement coordinator
register for BusinessAgreement
BusinessAgreement coordinator
completed
faulted
compensate
forget
Copyright Springer Verlag Berlin Heidelberg 2004

24. RosettaNet

25. RosettaNet Goals and scope of RosettaNet
Global, non-profit, business consortium of 400 vendors
eCommerce interfaces to align IT supply chain
Standardization efforts in the following areas
Business processes
RosettaNet Partner Interface Processes
Defines business documents, vocabulary and choreography of messages
PIPs are published by RosettaNet in a PIP Directory
Data format
RosettaNet Business Dictionary
Rosettanet Technical Dictionary
Messaging services
Rosettanet Implementation Framework (RNIF)

26. Partner Interface Process (PIP) Specifications
PIP specification includes
A technical dictionary
Message guideline
Two categories of PIP messages
Business action messages – e.g. Purchase Order; Billing statement
Business signal messages – e.g. acknowledgement messages related to business action messages
Process of developing a PIP specification
Model “as-is” business process and partner types identification
Re-engineer this model to support web-based interactions
Create a PIP Blueprint document of the re-engineered process showing partner types and interactions
Create a PIP protocol that can be implemented by system developers

27. PIP Specification views
Business Operational View
Known as the “action layer” describes the flow of interactions between entities
Functional Service View
Known as the “transaction layer” specifies the details of the message exchanges
Implementation Framework View
Known as the “service layer” details communication protocols and message format specifications

28. RosettaNet PIP 3A2 (Request Price and Availability)
:customer
:product supplier
start
<<SecureFlow>> price and availability response
<<RequestResponseActivity>> request price and availability
process price and availability request
<<SecureFlow>> price and availability request
[ fail ]
[ success ]
end
Business Process Flow Diagram
failed
Copyright Springer Verlag Berlin Heidelberg 2004

29. PIP definitions
Cluster 0 – RosettaNet support
Cluster 1 – Partner Product and Service Review
Cluster 2 – Product information
Cluster 3 – Order management
Cluster 4 – Inventory management
Cluster 5 – Marketing Information Management
Cluster 6 – Service and support
Cluster 7 - Manufacturing

30. transport protocols (TCP/IP and others) HTTP SMTP other (future) HTTPS
SSL
preamble header
delivery header
service header
service content
attachment 1
attachment n
MIME multipart/related envelope
headers
business process payload
RosettaNet Business
message components
And Protocol Stack
Copyright Springer Verlag Berlin Heidelberg 2004

31. Other standards related to Coordination Protocols
XML Common Business Library (xCBL)
CommerceOne developed this specification
For example, develops an EDI for order management, package, transport and invoicing using XML
Includes notions of roles – buyer, seller
Electronic Business Using eXtensible Markup Language (ebXML)
Sponsored by UN/CEFACT – UN that is responsible for EDI
Specifications for how electronic commerce should be specified, documented, and conducted.
Web service choreography interface (WSCI