softDevProcesses

softDevProcesses - CSE 216: Software Engineering CSE 216:...

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Unformatted text preview: CSE 216: Software Engineering CSE 216: Software Engineering--- Software Development Processes Gang Tan Department of Computer Science & Engineering Lehigh University 1 * Many slides courtesy of Blank and Constantinides Readings Readings c Chapter 1 and chapter 2 of the textbook 2 Software development process has Software development process has stages stages c Requirements and analysis: Establish the applications goals and constraints in consultation with users c Design: Establish the systems architecture plementation and unit testing: c Implementation and unit testing: Realize the design as a set of programs or program units Unit testing verifies that each unit meets its specification c Integration and system testing: Integrate the program units and test as a complete system c Maintenance: Correct errors, improve implementation, and enhance the systems services as new requirements are discovered 3 Relative costs to fix errors: Relative costs to fix errors: What can you infer from this graph? What can you infer from this graph? 40 50 60 70 80 Cost 10 20 30 Requirements Design Implementation Testing Maintenance Cost to fix an error increases as it is found later and later in the software lifecycle 4 What is the primary driver of What is the primary driver of software costs? software costs? What can you infer from the following graph? 3% 8% 7% 5% Requirements -- 3% Design -- 8% Implementation -- 7% 5 15% 67% Testing -- 15% Maintenance -- 67% Most money and effort spent in testing and maintenance But: 85% of errors are introduced during requirements analysis and design Waterfall model of software Waterfall model of software process process c Cascades from one stage down to the next, in stately, lockstep, glorious 6 order. Gravity only allows the waterfall to go downstream; its very hard to swim upstream Waterfall model of software Waterfall model of software process process c Department of Defense contracts prescribed this model for software deliverables for many years, in DOD Standard 2167-A 7 Why would managers like the Why would managers like the waterfall model? waterfall model? c Minimizes change, maximizes predictability c Costs and risks are more predictable ach stage has milestones and c Each stage has milestones and deliverables: project managers can use to gauge how close project is to completion c Sets up division of labor: many software shops associate different people with different stages 8 Drawbacks of the waterfall model Drawbacks of the waterfall model c The reality is that not only does software change, but change happens during the process Realistic models are not strictly linear, but allow for cycles c Fail to treat software a problem-solving process Unlike hardware, software development is not a manufacturing but a creative process Manufacturing processes really can be linear sequences, but creative processes usually involve back-and-forth activities such as revisions...
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softDevProcesses - CSE 216: Software Engineering CSE 216:...

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