Measurement (II)1 Measurement - Productivity, Estimation, Effort Advanced Software Engineering COM360 University of Sunderland © 1998

Measurement (II)2 Productivity (i) There are two general approaches: i) lines of code per person-month (LOC/pm) -only useful for productivity during coding!, language dependency, defining a LOC ii) function points (FP/pm) derived as soon as specification is done, synthetic measure, complexity factors

Measurement (II)3 Function Points 5 function types 3 levels of complexity 14 technical complexity factors synthetic (derived) measures are difficult to validate, main application: effort prediction, oriented to commercial systems not real time or embedded systems

Measurement (II)4 Productivity (ii) 4What about the other factors? -productivity in testing: no. of defects found -productivity to a project manager: milestones 4The measure of productivity should be dependent on the phase 4Teams, tools, methods 4Personnel experience and capability

Measurement (II)5 Estimating An estimate is defined as the median of a known distribution (it divides the area into two equal halves). Break a major task into smaller tasks, for each task: best case, expected, worst case, derive (best, exp, worst) values for major task

Measurement (II)6 Estimation Accuracy Accuracy is often represented by ‘relative error (RE)’ RE = (actual - estimate) / actual when actual>estimate : RE is... when actual<estimate : RE is...

Measurement (II)7 Estimation Problems 4Novelty of application Õnew problem to solve, Õdifferent hardware platform, Õdifferent OS and tools, Õdifferent development team. 4‘Price to win’ - targets = estimates

Measurement (II)8 Approaches to Estimation 4Expert opinion - ‘three wise men/women’ 4Analogy - past project, identify differences, forces documentation 4Decomposition - task breakdown, recombine 4Models - key factors, maths formulae, (size) ( increasing formality as you move down)

Measurement (II)9 Models of Effort and Cost 4Size,S 4Productivity,p 4Economy of scale,e Effort = pS e

Measurement (II)10 Examples 4COCOMO effort, cost drivers, LOC, 3 levels of model(s,i,d) 4COCOMO stage decomposition, revised cost drivers 4SLIM - Rayleigh curve estimates, 4 stages