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Software Re-Creation From Legacy to Component Arie van Deursen.

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1 Software Re-Creation From Legacy to Component Arie van Deursen

2 09-09-1999CMG / ESTEC2 Software Duplication zPrograms  “Dit programma is grotendeels een kopie van het XY progamma ABCD123.” zSubsystems yCICS and BATCH functionality zFunctions & Computations zEntire systems

3 09-09-1999CMG / ESTEC3 Function Duplication Example zWhen is a year a leap year ?  Two (small) 100.000 LOC systems contained 8 different computations! return( (year%4 == 0 && year%100 != 0) || year%400 == 0 ) IF YY = 92 OR 96 MOVE 29 TO MD(2) END-IF

4 09-09-1999CMG / ESTEC4 Component Software Technology zAbstraction zSelection zSpecialization zIntegration Process z Create reusable assets z Support z Reuse z Manage AND ONLY ONCE! Kent Beck: Say it once!

5 09-09-1999CMG / ESTEC5 Financial Products zLoan, swap, future, FRA, … zIntroduce innovative products zBank’s backoffice hard to adapt zDescribe products at high level zGenerate (COBOL) code zAt MeesPierson, with CAP Gemini

6 09-09-1999CMG / ESTEC6 Domain-Specific Languages Product Specification Legacy Calls Cobol Routines VSAM data CICS screens... DSL Compiler Component Libarary

7 09-09-1999CMG / ESTEC7 Domain Engineering zIdentify potential reusable assets zDomain = family of systems z3 legacy + 3 future zEconomy of scope zOrganizational learning Application System Engineering Domain Engineering

8 09-09-1999CMG / ESTEC8 Organizational Domain Modeling (ODM) Plan Domain zstakeholders zdomain boundary decisions zexamples zcounter-examples Model Domain zdomain experts zreverse engineer legacy systems zlexicon of terms zcommonality zvariability Engineer Asset Base zscope zarchitect zimplement

9 09-09-1999CMG / ESTEC9 Reverse Engineering Tools Object Model Hypertext documentation Visualization Legacy Sources Fact Extractor Repository Abstract Combine Filter

10 09-09-1999CMG / ESTEC10 Small classes Large classes Field names Method nrs

11 09-09-1999CMG / ESTEC11 Summary Components: zAbstraction zSelection zSpecialization zIntegration z Domain-Specific Languages z Program Understanding Tools Domain Engineering: zComonality zVariability zEconomy of Scope zFamily of systems

12 09-09-1999CMG / ESTEC12 In Conclusion zRecommended Reading yMeyer: Object-Oriented Software Construction yBrooks: The Mythical Man Month yJacobson, et. al.: Software Reuse zQuote from Alan Kay: To be a good software engineer, you need the ability to feel pain CBD: essential for producing quality software

13 Questions?

14 09-09-1999CMG / ESTEC14 Component-Based Development: Keywords zObject-Oriented Application Framework zHot Spots zDesign Pattern zJava zObject Request Brokers, CORBA, DCOM zSoftware Architecture zUnified Modeling Language zN-Tier Systems

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