MG6088 - Software Project Management - PROJECT LIFE CYCLE AND EFFORT ESTIMATION
Basis for successful estimating:
A taxonomy of estimating methods:
Major Shortcomings of SLOC :
Some problems with estimating:
- Subjective nature of much of estimating
- It may be difficult to produce evidence to support your precise target
- Political pressures
- Managers may wish to reduce estimated costs in order to win support for acceptance of a project proposal
- Changing technologies
- these bring uncertainties, especially in the early days when there is a ‘learning curve’
- Projects differ
- Experience on one project may not be applicable to another
Basis for successful estimating:
- Information about past projects
- Need to collect performance details about past project: how big were they? How much effort/time did they need?
- Need to be able to measure the amount of work involved
- Traditional size measurement for software is ‘lines of code’ – but this can have problems
A taxonomy of estimating methods:
- Bottom-up - activity based, analytical
- Parametric or algorithmic models e.g. function points
- Expert opinion - just guessing?
- Analogy - case-based, comparative
- Parkinson and ‘price to win’
Parameters to be Estimated:
- Size is a fundamental measure of work
- Based on the estimated size, two parameters are estimated:
- Effort
- Duration
- Effort is measured in person-months:
- One person-month is the effort an individual can typically put in a month.
Measure of Work:
- The project size is a measure of the problem complexity in terms of the effort and time required to develop the product.
- Two metrics are used to measure project size:
- Source Lines of Code (SLOC)
- Function point (FP)
- FP is now-a-days favoured over SLOC:
- Because of the many shortcomings of SLOC.
Major Shortcomings of SLOC :
- Difficult to estimate at start of a project
- Only a code measure
- Programmer-dependent
- Does not consider code complexity
