Section 5
Activity-Based Software Cost Estimating

Software cost estimating at the activity level, or micro-estimating, is far more accurate than macro-estimating, but is also more difficult. The advantages of activity-based estimation are twofold: (1) key activities will not be accidentally left out, and (2) estimating errors, if they occur, tend to stay local within a specific activity rather than affecting the entire suite of activities.

This section explores the software cost-estimating implications of ten key software development activities:

Requirements

Prototyping

Design and specifications

Design inspections

Coding

Code inspections

Change management and configuration control

Testing

User documentation and project documentation

Project management

These ten activities comprise a minimum set for activity-based software cost estimating, although not every one of these activities occurs on every project. Also, most of these ten activities occur with very high frequency and, hence, can be encountered on many large software development projects.

However, the maximum set of activities for very large systems is more than 25 activities, which can be decomposed into many hundreds of sub-activities and tasks. Discussing the implications of estimating 25 or more software activities would require a book more than twice as large as the current volume.