lect3 - 1.264 Lecture 3 Time and resource estimation Rapid...

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1.264 Lecture 3 Time and resource estimation
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Rapid implementation What do you need? High certainty in meeting a schedule constraint Runaway prevention (with bad past history) Predictability (tied to budget, other programs) Lowest cost Desire for free overtime (startups, cheap companies) These are not the same problem Choose a method appropriate to the problem
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Schedule fundamentals SCHEDULED COMPLETION DATE Most projects are scheduled in one of these zones Probability of completing exactly on the scheduled date Most projects are completed in one of these zones Because of unrealistic expectations, most projects will be perceived as slow even if they are completed in the efficient or rapid zones. Figure by MIT OCW.
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Where the time goes Activity Small project Large project (2,500 lines of code) (500,000 lines of code) Architecture/design 10% 30% Detailed design 20% 20% Implementation 25% 10% Unit test 20% 5% Integration 15% 20% System test 10% 15% Soft spots: Rework Feature creep Bad requirements Fuzzy front end (delays in approval, staffing…)
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Lifecycle models Pure waterfall Code-and-fix (“code like hell”) Spiral Modified waterfall Evolutionary prototyping Staged delivery Design to schedule Evolutionary delivery Design to tools Commercial off the shelf software
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Waterfall Software Concept Requirements Analysis Architectural Design Detailed Design Coding and Debugging System Testing The pure waterfall model. The waterfall model is the most well known lifecycle model and provides good development speed in some circumstances. Other models, however, often provide greater development speed. Figure by MIT OCW.
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Figure by MIT OCW. Estimation± Figure by MIT OCW.
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Estimation steps Estimate size of project: Methods/behaviors (formerly function points) to be configured, modified, written and/or implemented Lines of code Estimate effort (person-months) Estimate schedule (calendar-months) Estimate team size as (person-months / calendar- months) Provide estimates in ranges and refine for increasing precision as project progresses
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Project size estimation Count: Inputs: Web pages, forms, dialogs, messages, XML documents Outputs: Web pages, reports, graphs, messages, XML documents Inquiries: simple Web inputs, generally producing a single output Logical internal files: tables, views or files in database External files: tables or files used from other systems or databases
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Method (function point) multipliers Low Complexity Program Characteristic Medium Complexity High Complexity Number of inputs x 3 x 4 x 6 Number of outputs x 4 x 5 x 7 Inquiries x 3 x 4 x 6 Logical internal files x 7 x 10 x 15 External interface files x 5 x 7 x 10 FUNCTION POINTS Figure by MIT OCW.
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Effort estimation (method/function point example) Low Complexity Example of Computing the Number of Function Points Program Characteristic Medium Complexity
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lect3 - 1.264 Lecture 3 Time and resource estimation Rapid...

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