ch18 - Software Reuse Ian Sommerville 2004 Software...

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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 18 Slide 1 Software Reuse
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 18 Slide 2 Objectives To explain the benefits of software reuse and some reuse problems To discuss several different ways to implement software reuse To explain how reusable concepts can be represented as patterns or embedded in program generators To discuss COTS reuse To describe the development of software product lines
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 18 Slide 3 Topics covered The reuse landscape Design patterns Generator based reuse Application frameworks Application system reuse
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 18 Slide 4 Software reuse In 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 but it is now recognised that to achieve better software, more quickly and at lower cost, we need to adopt a design process that is based on systematic software reuse.
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 18 Slide 5 Reuse-based software engineering Application system reuse The whole of an application system may be reused either by incorporating it without change into other systems (COTS reuse) or by developing application families. Component reuse Components of an application from sub-systems to single objects may be reused. Covered in Chapter 19. Object and function reuse Software components that implement a single well- defined object or function may be reused.
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 18 Slide 6 Reuse benefits 1 Increased dependability Reused software, that has been tried and tested in working systems, should be m ore dependable than new software. The initial use of the software reveals any design and implementation faults. These are then fixed, thus reducing the number of failures when the software is reused. Reduced process risk If software exists, there is less uncertainty in the costs of reusing that software than in the costs of development. This is an important factor for project management as it reduces the margin of error in project cost estimation. This is particularly true when relatively large software components such as sub-systems are reused. Effective use of specialists Instead of application specialists doing the same work on different projects, these specialists can develop reusable software that encapsulate their knowledge.
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©Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 18 Slide 7 Reuse benefits 2 Standards compliance Some standards, such as user interface standards, can be implemented as a set of standard reusable components. For example, if menus in a user interfaces are implemented using reusable components, all applications present the same menu
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ch18 - Software Reuse Ian Sommerville 2004 Software...

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