Empirical Estimation Models Based upon historic data Basic Structure E = A + B * (ev) C where A, B, c are empirical constants ‘ev’ is the effort in terms of lines of code or FP ‘E’ is the effort in terms of person months COCOMO - COnstructive COst MOdel E = 3.2 (KLOC) 1.05

Software Engineering II Lecture 17 Fakhar Lodhi

Recap

Software Project Estimation Project adjustment components –Problem complexity –Staff experience –Development environment and tools Factors – human, technical, environmental, political Estimation is difficult – not an exact science

Summary of Today’s Lecture

The Software Equation It’s a Dynamic Multivariable Estimation Model Assumes a specific distribution of effort over the life of the software development project Derived from productivity data collected for over 4000 projects

E = [LOC x B0.333/P]3 x (1/t4) E – effort in person months or person years t – project duration in months or years B – special skill factor –Increases slowly as the need for integration, testing, QA, documentation, management skills grow P – productivity parameter –Overall process maturity and management practices –The extent to which good SE practices are used –The level of programming language used –The state of the software environment –The skills and experience of the software team –The complexity of the application

Buy versus build Develop specification for function and performance of the desired software. Define measurable characteristics whenever possible Estimate internal cost and time to develop Select 3-4 candidate applications that best meet your specifications Select reusable software components that will assist in constructing the required application

Buy versus build Develop comparison matrix that presents a head-to- head comparison of key function. Alternatively, conduct benchmark tests to compare candidate software Evaluate each software package or component based on past product quality, vendor support, product direction, reputation, etc Contact other users of the software and ask for opinion

Buy versus build Delivery date Development Cost –Acquisition + customization Maintenance Cost