1. Service-Oriented Computing: Semantics, Processes, Agents
August 2004
Chapter 4: Enterprise Architectures
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
Enterprise Integration
J2EE
.NET
Model Driven Architecture
Legacy Systems
Chapter 4
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
© Singh & Huhns

3. J2EE Technology Chapter 4
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

4. .NET Technology Chapter 4
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

5. .NET Web Services COBOL Web service for multiplication
webservice language=''COBOL'' %>
CLASS-ID. MULTIPLICATIONSERVICE.
FACTORY.
PROCEDURE DIVISION.
METHOD-ID. MULTIPLY.
DATA DIVISION.
LINKAGE SECTION.
01 VAL-1 PIC S9(9) COMP-5.
02 VAL-2 PIC S9(9) COMP-5.
01 PRODUCT PIC S9(9) COMP-5.
PROCEDURE DIVISION USING BY VALUE VAL-1 VAL-2 RETURNING PRODUCT.
COMPUTE PRODUCT = VAL-1 * VAL-2.
END METHOD MULTIPLY.
END FACTORY.
END CLASS MULTIPLICATIONSERVICE.
Chapter 4
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

6. Service-Oriented Computing: Semantics, Processes, Agents
August 2004
Legacy Systems
A pejorative term for computing systems that
Run on obsolete hardware and nonstandard networks
Run poorly documented, difficult-to-maintain software
Consist of poorly modeled databases
Support rigid user interfaces
Notice that “legacy systems” is not synonymous with “mainframe”
Mainframes have had a resurgence in the last decade: no longer obsolete hardware; often support modern OSs (Linux); not necessarily poorly modeled or rigid (though some elements are obsolete or arcane)
Chapter 4
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
© Singh & Huhns

7. How Legacy Systems Arise
Service-Oriented Computing: Semantics, Processes, Agents
August 2004
How Legacy Systems Arise
Proprietary software
Not supporting industry standards
Sold by vendors who hope to lock in the market through incompatibility
Meaning embedded procedurally in the code
Ad hoc changes to software in response to
Changing requirements (laws, regulations, competition, or other business needs)
Bugs
Chapter 4
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
© Singh & Huhns

8. Legacy Systems: Pros and Cons
Service-Oriented Computing: Semantics, Processes, Agents
August 2004
Legacy Systems: Pros and Cons
Fulfill crucial business functions
Run the world’s airline reservation systems
Run most air traffic control programs
Have loyal users, reluctant to migrate
Represent huge investments in time and money
Complicate reuse and sharing of data
Cause redundancy, wasted effort, and integrity violations
Chapter 4
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
© Singh & Huhns

9. Service-Oriented Computing: Semantics, Processes, Agents
August 2004
Migration
Updating technology is
Essential
A continual process
All at once?
Expensive
Risky
Brittle
Frustrating for users
Gradual change: dismantle legacy and build desired system hand-in-hand
Install and test piecemeal
Chapter 4
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
© Singh & Huhns

10. Service-Oriented Computing: Semantics, Processes, Agents
August 2004
Applying Services
New Service
Services Refactored
from Legacy Backend
Application
Legacy
Backend
Legacy Interface
Chapter 4
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
© Singh & Huhns

11. Chapter 4 Summary Services must fit into existing architectures
J2EE and .NET are architecturally quite similar
Legacy systems provide the basis for many modern services
They host key data and processes
Interoperating with them is nontrivial
Challenge: refactoring legacy capabilities to derive best value from resulting services
Chapter 4
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns