Transcript Chapter 4: Enterprise Architectures

Chapter 4:
Enterprise Architectures
Service-Oriented Computing: Semantics, Processes, Agents
– Munindar P. Singh and Michael N. Huhns, Wiley, 2005
Highlights of this Chapter
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Chapter 4
Enterprise Integration
J2EE
.NET
Model Driven Architecture
Legacy Systems
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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J2EE Technology
RMI, IIOP
CORBA Client
Java Applet in
Browser
Entity Bean
RMI
RMI
Java
Applications
(Swing, AWT)
RMI
XML, HTML, HTTP (SSL)
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Session
Bean
J2EE
Connector
Legacy
System
EJB Server
Web Browser
Servlet JSP
Relational
DBMS
Java Message
Service
Java Naming and
Directory
Interface
Operating System (Windows,
Linux, Mac, Solaris…)
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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.NET Technology
ADO,
OCEDB,
ODBC
CORBA Client
Relational
DBMS
Shared Property
Manager
ActiveX Control
in Browser
COM+
COMPONENT
Applications
Babylon
Integration
Server
Legacy
System
Microsoft Transaction Server
Web Browser
XML, HTML, HTTP (SSL)
IIS/ASP
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Microsoft
Active Directory
Message
Queue
Windows Operating System
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.NET Web Services
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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
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Legacy Systems
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A pejorative term for computing systems that
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Notice that “legacy systems” is not
synonymous with “mainframe”
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Chapter 4
Run on obsolete hardware and nonstandard networks
Run poorly documented, difficult-to-maintain software
Consist of poorly modeled databases
Support rigid user interfaces
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)
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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How Legacy Systems Arise
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Proprietary software
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Meaning embedded procedurally in the code
Ad hoc changes to software in response to
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Not supporting industry standards
Sold by vendors who hope to lock in the market
through incompatibility
Changing requirements (laws, regulations,
competition, or other business needs)
Bugs
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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Legacy Systems: Pros and Cons
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Fulfill crucial business functions
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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
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Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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Migration
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Updating technology is
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All at once?
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Essential
A continual process
Expensive
Risky
Brittle
Frustrating for users
Gradual change: dismantle legacy and build desired
system hand-in-hand
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Chapter 4
Install and test piecemeal
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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Applying Services
New Service
Application
Services Refactored
from Legacy Backend
Legacy
Backend
Legacy
Interface
Chapter 4
Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns
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Chapter 4 Summary
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Services must fit into existing
architectures
J2EE and .NET are architecturally quite
similar
Legacy systems provide the basis for
many modern services
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Chapter 4
They host key data and processes
Interoperating with them is nontrivial
Challenge: refactoring legacy capabilities to
derive best value from resulting services
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