1. CS 493/693: Distributed Systems Programming
V. “Juggy” Jagannathan
CSEE, West Virginia University
March 7, 2005

2. Chapter 3: Enterprise Application Integration
Web Services: Concepts, Architectures and Applications
G. Alonso et. al.
Springer Verlag

3. From Middleware to Enterprise Application Integration (EAI)
Middleware and 3-tier architectures addressed the need to integrate multiple resources (typically databases whose interface was standardized using ODBC or JDBC type interfaces)
EAI refers to the integration faced when dealing with multiple middleware systems to provide enterprise-wide functionality

4. EAI: Application Example
quotation
supplier and
customer mgmt
order
processing
procurement
shipment
management
financial
Manual process of implementing a supply-chain system
Copyright Springer Verlag Berlin Heidelberg 2004

5. Need for message brokers
dispatcher
inventory management
ERP
shipping
message-oriented middleware
month-end closing
new PO
With RPC or message-based interoperability, applications need to be
Changed if they need to interoperate with a new system (dashed)
Copyright Springer Verlag Berlin Heidelberg 2004

6. Extending basic Message-Oriented Middleware (MOM)
message broker core
sender
receiver
message broker
with message brokers, custom message routing logic can be defined at the message broker level or at the queue level
in basic MOM it is the sender who specifies the identity of the receivers
Message brokers enable users to define custom message routing logic
Copyright Springer Verlag Berlin Heidelberg 2004

7. Publish/Subscribe Interaction Model
dispatcher
(publisher)
inventory management
(subscriber)
ERP
shipping
message broker
month-end closing
new PO
Copyright Springer Verlag Berlin Heidelberg 2004

8. Distributed Administration of a Message Broker
message broker MB-A
message broker MB-B
client …
message broker MB-C
administrative domain A
administrative domain B
administrative domain C
Copyright Springer Verlag Berlin Heidelberg 2004

9. High-level architecture of typical EAI systems
DBMS applications
message broker
SmartQuotation
adapter
database
SmartForecasting
XYZ
integrating application (contains the composition logic)
Copyright Springer Verlag Berlin Heidelberg 2004

10. Example use of message broker
at systems startup time (can occur in any order, but all must occur before RFQs are executed)
A: subscription to message quote
B: subscription to message quoteRequest
C: subscription to message newQuote
at run time: processing of a request for quote.
1: publication of a quoteRequest message
2: delivery of message quoteRequest
3: synchronous invocation of the getQuote function
4: publication of a quote message
5: delivery of message quote
6: publication of a newQuote message
7: delivery of message newQuote
8: invocation of the createForecastEntry procedure
RFQ processing A 1 5 6
message broker B 2 4 C 7
SmartQuotation
adapter
SmartForecasting
adapter 3 8
SmartQuotation
SmartForecasting
Copyright Springer Verlag Berlin Heidelberg 2004

11. Critical view of message brokers
On the plus side
Lower development costs
Lower opportunity costs
Lower maintenance effort
On the negative side
Expensive tool suite
Adapters may not be easy to build

12. Workflow Management Systems

13. Historical background on workflow systems
WfMS – work flow management systems
Evolved from supporting “office automation”
Types of workflows
Administrative workflows (travel reimbursement processing)
Production workflows
Commercial platforms
WebSphere MQ workflow (IBM)
Vitria Businessware
Tibco Business Process Modeling (BPM)
BEA Web Logic
Microsoft BizTalk Orchestration
Standardization effort – Workflow Management Coalition (WfMC)

14. Workflow definitions
Business Process – a collection of activities that are performed by humans or software applications
Work node – work that needs to be done
Routing node – define the order in which work can be carried out
Start and completion nodes – start and end points of workflows
Workflow instance – an instance of a specific workflow process

15. Workflow model for a quotation system
check if
offered product
Offered=false
check if
worth proceeding
Offered=true
else
GoAhead=true
get quote from quotation system
variables:
QuoteReferenceNumber: int
Customer: String
Item: String
Quantity: int
RequestedDeliveryDate: Date
DeliveryAddress: String
GoAhead: Bool
ContractExists: Bool
Offered: Bool
ContractExists=false
get quote
from supplier
ContractExists=true
update quotation system
send quote
to customer
enter quote
in forecasting system
Copyright Springer Verlag Berlin Heidelberg 2004

16. Scheduling and managing workflows
resource broker
resource 1 5 3 4
workflow engine
resource 2
completed work items
inbound queue 1 2
resource n
workflow definitions
outbound queues
workflow designer
Copyright Springer Verlag Berlin Heidelberg 2004

17. Recovering from failures
Forward recovery
Backward recovery
Sagas or compensating activity
Exception handling languages
Deadlines and deadline expiration

18. Workflow and EAI technologies combined
WfMS
WfMS adapter
message broker
SmartQuotation
adapter
database
adapter
SmartForecasting
adapter
adapter
XYZ
adapter
SmartQuotation
DBMS applications
XYZ
SmartForecasting
Copyright Springer Verlag Berlin Heidelberg 2004

19. Workflow summary
Expensive and complicated to implement
Useful in applications that are highly repetitive
But the same applications can be done better with conventional middleware
Nevertheless, they constitute a generic approach to a lot of commercial workflow problems.