Measurement’s Text Models
Of the three types of Measurement Models, Text models tend to be the least effective, but the most common. It is difficult to adequately describe complex situations and dynamics using just words.
Here is a text model for software development:
Effort: The time required to develop a product, expressed as increments of staff development time (e.g., staff months/hours). In general, effort is a function of size and results in cost.
Features: The requirements of the product to be developed.
Size: The magnitude of the product to be developed. In general, size is a function of features.
Defects: The incompleteness of the product. In general, defects are a function of size and schedule.
Schedule: The total development time; completion times for principal milestones. In general, schedule is a function of effort and resources.
Resources: The number of developers applied to the product development.
This text model has advantages and disadvantages. Each item is clearly defined and easy to understand, but the relationships between items may be difficult to visualize. But notice that this text model describes software development in such a way that we can discuss it, measure it, and predict it: if the size changes, the number of defects will change. This text model gives structure to the abstract concept of software development.