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DoD Software Summit,2001 Strategic Software Design Kevin Sullivan University of Virginia Department of Computer Science
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DoD Software Summit,2001 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
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DoD Software Summit,2001 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 –decentralized control over search
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DoD Software Summit,2001 DSM: Non-Modular Design Design parameters (and design tasks) Parameter interdependencies (implied communications)
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DoD Software Summit,2001 DSM: Proto-Modular Design Proto-modules (and corresponding aggregate tasks)
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DoD Software Summit,2001 DSM: Modular Design design rule constrains search decouples taskscreating independent modules, and valuable substitution options
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DoD Software Summit,2001 DSM in Environment (EDSM) Sub-Optimal Modular Design Design rules sensitive to change in environment
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DoD Software Summit,2001 EDSM for High Value Modularity Design rules invariant under change in environment
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DoD Software Summit,2001 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]
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DoD Software Summit,2001 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
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DoD Software Summit,2001
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Parnas 72: Traditional Modularity FUNCTION SIGNATURES DATA STRUCTURES ALGORITHMS
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DoD Software Summit,2001 Parnas 72: IH Modularity ADT INTERFACES DATA STRUCTURES & ALGORITHMS
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DoD Software Summit,2001 EDSM: Traditional Modularity ENVIRONMENT PARAMETERS IMPACT OF EPs ON DESIGN RULES AND ON INDEPENDENT MODULES
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DoD Software Summit,2001 EDSM: IH Modularity INVARIANCE OF DESIGN RULES UNDER ENVIRONMENTAL CHANGE
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DoD Software Summit,2001 Comparative Net Options Value NOV = E (Benefit of k Experiments) – Cost of k Experiments – Ripple Costs
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DoD Software Summit,2001 Parnas 72: Non-Modular Design IN SHIFT SORT OUT CTL
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