02-Design - User-Centered Design 1 Waterfall Model...

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1 1 User-Centered Design 2 Waterfall Model ± Characterized by • Feedback loops • Testing and validation • Documentation-driven ± Advantages • Enforced disciplined approach ± Disadvantages • “I know this is what I asked for, but it isn’t really what I wanted.”
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2 3 Waterfall Model Is Bad for User Interface Design ± User interface design is risky • So we are likely to get it wrong ± Users are not involved in validation until acceptance testing • So we won’t find out until the end ± UI flaws often cause changes in requirements and design • So we have to throw away carefully-written and tested code 4 Iterative Design ± Manage the inherent risk in user interface design
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3 5 Iterative Design the Wrong Way ± Every iteration corresponds to a release • Evaluation (complaints) feeds back into next version’s design ± Using paying customers to evaluate usability • They won’t like it • They won’t buy version 2 6 Spiral Model
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4 7 Spiral Model ± Radial dimension: cumulative cost to date ± Angular dimension: progress through the spiral ± Each cycle of the spiral corresponds to a phase ± A phase begins in the top left quadrant by determining • Objectives of that phase • Alternatives for achieving those objectives • Constraints imposed on those alternatives ± This process results in a strategy for achieving those objectives ± The strategy is analyzed from the viewpoint of risk ± Development starts from bottom right quadrant • This quadrant corresponds to waterfall model 8 Early Prototypes Can Detect Usability Problems
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5 9 Iterative Design of User Interfaces ± Early iterations use cheap prototypes • Parallel design is feasible: build and test multiple prototypes to explore design alternatives ± Later iterations use richer implementations, after UI risk has been mitigated ± More iterations generally means better UI ± Only mature iterations are seen by the world 10 User-Centered Design ± Iterative design ± Early focus on users and tasks • User analysis: who the users are • Task analysis: what they need to do • Involving users as evaluators, consultants, and sometimes designers ± Constant evaluation • Users are involved in every iteration • Every prototype is evaluated
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02-Design - User-Centered Design 1 Waterfall Model...

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