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Most textbooks and most of today’s software engineering models are based on the ‘waterfall model’ for delivery. This can take several forms, but the principle characteristics are :
• all planning is oriented towards a single delivery date. If phased delivery is used, the phase units are substantial, and there is no formal concept of ‘reworking’ unsatisfactory phases.
• all analysis and design are done in detail, before coding and test.
The delivery date is normally one or more years after project start. There may be some effort to improve the design by means of prototypes. But these prototypes will usually be ‘throw away.’ There will be little or no real useful work by users done on them.