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Legacy Systems Migration in Service-Oriented Computing

Explore challenges and benefits of migrating legacy systems to modern services, including J2EE and .NET technologies. Learn the pros and cons, migration strategies, and service applications. Understand the importance of legacy systems in modern service architectures and the complexities of refactoring legacy capabilities. Discover essential tips and considerations for a successful migration process.

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Legacy Systems Migration in Service-Oriented Computing

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  1. Chapter 4:Enterprise Architectures Service-Oriented Computing: Semantics, Processes, Agents– Munindar P. Singh and Michael N. Huhns, Wiley, 2005

  2. Highlights of this Chapter • Enterprise Integration • JEE • .NET • Model Driven Architecture • Legacy Systems Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

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

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

  5. .NET Web Services • COBOL Web service for multiplication (Mike’s joke) <%@ 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. Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

  6. Legacy Systems • A pejorative term for computing systems that • Run on obsolete hardware and nonstandard networks • Run poorly documented, unmaintainable 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 (some elements are obsolete or arcane) • Most problems are with software whether on mainframes or other machines Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

  7. How Legacy Systems Arise • Proprietary software: • not supporting industry standards • (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, because of changes in laws, regulations, competition, or other business needs • bugs Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

  8. Legacy Systems: Pros and Cons • Fulfill crucial business functions • Run the world’s airline reservation systems • Run most air traffic control programs • Have dedicated users • Represent huge investments in time and money • Complicate reuse and sharing of data and programs cause redundancy, wasted effort, and integrity violations Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

  9. 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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

  10. Applying Services New Service Services Refactored from Legacy Backend Application Legacy Backend Legacy Interface Error: services at too coarse a granularity Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael 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 Service-Oriented Computing: Semantics, Processes, Agents - Munindar Singh and Michael Huhns

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