pyright Nancy Leveson, Sept 1999 Reuse (Assume have source code, not a commercial product) Ariane 5. Therac-25. British AtC Expectation Significantly lower development costs and time. Amortize costs among all users or uses Assumptions Will be reused enough to recoup extra costs Can easily and cheaply integrate components into a new environment(interoperability)
Copyright Nancy Leveson, Sept. 1999 Reuse (Assume have source code, not a commercial product) Ariane 5, Therac-25, British ATC, ... Expectation: Significantly lower development costs and time. Amortize costs among all users or uses. Assumptions: Will be reused enough to recoup extra costs Can easily and cheaply integrate components into a new environment (interoperability). � c
Reuse: Empirical data High reuse in some limited environments, not widespread however NASA Goddard study Garlan Allen Ockerbloom Performance problems(from large size and complexity) Complexity frequently inappropriate for tasks performed Trouble fitting components together In some cases, took significant reengineering to make the interoperate properly Maintaining synthesized system difficult in absence of low-level understanding
Copyright Nancy Leveson, Sept. 1999 Reuse: Empirical Data High reuse in some limited environments, not widespread c however. NASA Goddard Study Garlan, Allen, Ockerbloom: Performance problems (from large size and complexity) Complexity frequently inappropriate for tasks performed. Trouble fitting components together. In some cases, took significant reengineering to make the interoperate properly. Maintaining synthesized system difficult in absence of low-level understanding. �
Reuse: Empirical Data Siemens(hardware ASICs)reuse study Time to build a reusable component can be 120-150% of time needed to develop component for single use (excludes documentation) For reusuable component, needed to develop new documentation - took one to two times the effort of designing the component Overhead to develop a reusable component(design+ doc recaptured after fifth use Frequency of reuse increases with degree of comprehensibility Habitability even more important: measure of how"at home a potential user of reusable component feels. Highly subjective but effect even greater than that of comprehensibility
Copyright Nancy Leveson, Sept. 1999 Reuse: Empirical Data (2) Siemens (hardware ASICs) reuse study: Time to build a reusable component can be 120-150% of time needed to develop component for single use (excludes documentation). For reusuable component, needed to develop new documentation -- took one to two times the effort of designing the component. Overhead to develop a reusable component (design + doc) c recaptured after fifth use. Frequency of reuse increases with degree of comprehensibility. Habitability even more important: measure of how "at home" a potential user of reusable component feels. Highly subjective but effect even greater than that of comprehensibility. �
opyright Nancy Leveson, Sept. 1999 Reuse: Technical issues Configuration control problems May change continuously(any developer may be able to check out and change) Unneeded functionality(interoperability and performance issues) May need to write software utilities(restrictive wrappers) to restrict functionality Much of savings may be offset by need for more testing (Weyuker) Debugging may be significantly more difficult(Weyuker) Longevity --does potential for reuse decrease over time? Reuse designs rather than finished products?
c Copyright Nancy Leveson, Sept. 1999 Reuse: Technical Issues Configuration control problems May change continuously (any developer may be able to check out and change). Unneeded functionality (interoperability and performance issues) May need to write software utilities (restrictive wrappers) to restrict functionality. Much of savings may be offset by need for more testing (Weyuker) Debugging may be significantly more difficult (Weyuker) Longevity -- does ppotential for reuse decrease over time? Reuse designs rather than finished products? �
Reuse: Other Management issues(e. g, reward structures) Platforms and reuse at Xerox(hopefully, one of the Xerox students can tell us about this) One organization within Xerox reports they use half dozen different software platforms to build half dozen different products Achieve approximately 80-90%reuse other comments or experiences?
Copyright Nancy Leveson, Sept. 1999 c Reuse: Other Management issues (e.g., reward structures) Platforms and reuse at Xerox (hopefully, one of the Xerox students can tell us about this). One organization within Xerox reports they use half dozen different software platforms to build half dozen different products. Achieve approximately 80-90% reuse Other comments or experiences? �