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Strategic Software Design

Strategic Software Design. Kevin Sullivan University of Virginia Department of Computer Science. Overview. Value added is overriding goal of design How do technical choices create value? Missing even basic science in this area Objective: enable design for value added. Example.

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Strategic Software Design

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  1. Strategic Software Design Kevin Sullivan University of Virginia Department of Computer Science DoD Software Summit,2001

  2. Overview • Value added is overriding goal of design • How do technical choices create value? • Missing even basic science in this area • Objective: enable design for value added DoD Software Summit,2001

  3. Example • Still don’t understand modularity well enough • What is it? • design structure matrix [Ulrich, Eppinger] • design rules [Baldwin, Clark] • How does it add value? • real options to search design space • decentralizedcontrol over search DoD Software Summit,2001

  4. DSM: Non-Modular Design Design parameters(and design tasks) Parameter interdependencies(implied communications) DoD Software Summit,2001

  5. DSM: Proto-Modular Design Proto-modules(and corresponding aggregate tasks) DoD Software Summit,2001

  6. DSM: Modular Design design ruleconstrains search decouples tasks creating independent modules,and valuable substitution options DoD Software Summit,2001

  7. DSM in Environment (EDSM)Sub-Optimal Modular Design Design rules sensitive to change in environment DoD Software Summit,2001

  8. EDSM for High Value Modularity Design rules invariant under change in environment DoD Software Summit,2001

  9. How Does It Add Value? • Overall value = • present value of function in environment + • present value of options to improve/adapt • Module-level option value (substitution case) • expected benefit: best of k candidate replacements – • cost of creating them – • cost of ripple effects • IBM360: 25X in options value! [B&C 2000] DoD Software Summit,2001

  10. Concluding Comments • Aim for generalized concept of modularity • well beyond inadequate OO model • E.g., to aspect-oriented modularity • power, real time response, hardware … • Options valuation model • certainly not proven for production use • sufficient to capture seminal results [Parnas72] • Insights into drivers of design & industry dynamics • Exploring tool support • Make DSMs scale with hierarchical design parameters DoD Software Summit,2001

  11. DoD Software Summit,2001

  12. Parnas 72: Traditional Modularity FUNCTIONSIGNATURES DATA STRUCTURES ALGORITHMS DoD Software Summit,2001

  13. Parnas 72: IH Modularity ADTINTERFACES DATA STRUCTURES &ALGORITHMS DoD Software Summit,2001

  14. EDSM: Traditional Modularity ENVIRONMENTPARAMETERS IMPACT OF EPsON DESIGN RULES AND ONINDEPENDENTMODULES DoD Software Summit,2001

  15. EDSM: IH Modularity INVARIANCE OF DESIGN RULES UNDER ENVIRONMENTALCHANGE DoD Software Summit,2001

  16. Comparative Net Options Value NOV = E (Benefit of k Experiments) – Cost of k Experiments – Ripple Costs DoD Software Summit,2001

  17. Parnas 72: Non-Modular Design IN SHIFT SORT OUT CTL DoD Software Summit,2001

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