Estimation techniques - estimation using use cases

We have read about estimation techniques like problem and process based estimation techniques. There is another estimation approach that uses use cases which provide insight into software scope and requirements. However, it is somewhat difficult to develop an estimation technique using use cases.

- There is no standard format or style in which use cases can be described because there are many different formats and styles that a use case can use.
- The complexity of the functions are not addressed by the use cases.
- Complex behavior like interactions among many functions and features are not described by the use cases.
- Use cases are used to represent the user's view of the software.

Use case estimation technique for one person can require a lot of effort while use case estimation technique for some other person can be done in a day or two. According to Smith, use cases can be used for estimation but it is only possible and considered within the context of structural hierarchy that the use case describe.

- structural hierarchy can have not more than 10 use cases.
- each use case can have not more than 30 different scenarios.
- before using use case estimation, level within structural hierarchy is established, average length of each use case is computed, type of software is defined, rough architecture is considered.
- empirical data is used to establish lines of code or function point for each level.