Presentation on theme: "Sommerville, I., Software Engineering, Pearson, 9th Ed., 2010."— Presentation transcript:
1 Sommerville, I., Software Engineering, Pearson, 9th Ed., 2010. Software Process ModelsFebruary 19, 2012Sommerville, I., Software Engineering, Pearson, 9th Ed., 2010.
2 Overview Software Process Software Process Models Waterfall Model Incremental DevelopmentReuse Oriented Software Engineering
3 Software ProcessA software process is a set of related activities that leads to the production of a software productThere are many different software processes but all must include four activities:Software specificationSoftware design and implementationSoftware validationSoftware evolution
4 Software Process A software process may also include: Products (outcomes of a process activity)Roles (responsibilities of people)Pre- and post-conditionsSometimes, software processes are categorized as either plan-driven or agile processes
5 Software Process Models A software process model is a simplified representation of a software processEach process model represents a process from a particular perspective, and thus provides a partial information about that processProcess models covered:The waterfall modelIncremental developmentReuse-oriented software engineering
7 The Waterfall Model Separate identified phases in the waterfall model: Requirements analysis and definitionSystem and software designImplementation and unit testingIntegration and system testingOperation and maintenanceThe result of each phase is one or more documentsThe following phase should not start until the previous phase has finished (in practice, they overlap)
8 The Waterfall Model Advantage: the process is visible Documentation is produced at each phase. Benefit?Problem: Inflexible partitioning of the project into distinct stages makes it difficult to respond to changing customer requirementsUse: When the requirements are well-understood and changes will be fairly limited during the design process.
10 Incremental Development Incremental development is based on the idea of developing an initial implementation, exposing this to user comment and evolving it through several versions until an adequate (acceptable) system has been developedGenerally, the early increments of the system include the most important or most urgently required functionalityCan be either plan-driven, agile, or a mixture of both
11 Incremental Development Benefits:The cost of accommodating changing customer requirements is reducedIt is easier to get customer feedback on the development work that has been doneMore rapid delivery and deployment of useful software to the customer is possible
12 Incremental Development Problems:The process is not visibleManagers need regular deliverables to measure progressSystem structure tends to degrade as new increments are addedUnless time and money is spent on refactoring to improve the software, regular change tends to corrupt its structure.
13 Reuse-Oriented Software Engineering Based on systematic reuse where systems are integrated from existing components or COTS (Commercial-off-the-shelf) systemsProcess stages:Component analysisRequirements modificationSystem design with reuseDevelopment and integration
15 Reuse-Oriented Software Engineering Advantages:Reduce the amount of software to be developed, and thus reduce cost and risksFaster delivery of the softwareProblems:May lead to a system that does not meet the real needs of usersControl over the system evolution is lost
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