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Software Reuse Software Reuse Bài 7: Sử dụng lại trong phần mềm Objectives The benefits of software reuse and some reuse problems Different ways to implement software reuse Patterns of reuse COTS reuse COTS reuse Software product lines Topics covered The reuse landscape Design patterns Generator based reuse Application frameworks reuse Application frameworks reuse Application system reuse Reuse of software vs. other engineering Most engineering disciplines Systems are designed by composing existing components that have been used in other systems . Software engineering Has been more focused on original development Now recognised that we need to adopt a design used in other systems . need to adopt a design process that is based on systematic software reuse to achieve better software, more quickly and at lower cost, Reuse-based software engineering Application system reuse The whole of an application system may be reused by incorporating it without change into other systems (COTS reuse) by developing application families. by developing application families. Component reuse Components of an application from sub-systems to single objects may be reused. (Chapter 19.) Object and function reuse Single well-defined object or function may be reused Reuse benefits Increased dependability • Has been tried and tested in working systems • Design and implementation faults are fixed, thus reducing the number of future failures when reused. Reduced process risk • Costs of reusing lower than costs of development. • Easier for project cost estimation. process risk • Easier for project cost estimation. Standards compliance • User interface standards, can be implemented as a set of standard reusable components. • Improves dependability as users when use a familiar interface. Accelerated development • Speed up system production because both development and validation time should be reduced. Reuse problems Increased maintenance costs • Maintenance costs may be increased as the reused elements of the system may become increasingly incompatible with system changes. Lack of tool support • CASE toolsets may not support development with reuse. Not - invented - here • Re - write components to improve on the reusable Not - invented - here syndrome • Re - write components to improve on the reusable component. Creating and maintaining a component library • Maintain a reusable component library and ensuring the software developers can use it can be expensive. Managing reusable components • Software components have to be discovered in a library, understood and, sometimes, adapted to work in a new environment. The reuse landscape Many different approaches to reuse Not only system components From simple functions to complete application systems The reuse landscape covers the range of possible The reuse landscape covers the range of possible reuse techniques Design patterns Component frameworks Application product lines Aspect- oriented Component based Program libraries COTS integration Program generators Service- oriented Program libraries Legacy system wrapping Configurable applications Reuse planning factors Which reuse technique to use? The development schedule for the software The background, skills and experience of the development team The criticality of the software and its non-functional requirements The application domain The execution platform for the software Concept reuse Concept reuse described by more abstract an implementation independent way Two main approaches Two main approaches Design patterns Generative programming . Software Reuse Software Reuse Bài 7: Sử dụng lại trong phần mềm Objectives The benefits of software reuse and some reuse problems Different