Estimation techniques - Problem based Estimation

In software estimation, lines of code and function point metrics can be used in two ways:
- it can be used as an estimation variable that could size each element of the software.
- it can be used as baseline metrics that are collected from past projects and are used with the estimation variables to develop cost and effort.

Lines of code and function point are different techniques but there are some characteristics that are common. Project planning begins with scope of the software and software is decomposed into problem functions and are estimated individually and then lines of code and function point are estimated for each function.

Baseline metrics are applied to estimation variable and cost and effort is derived. It should be kept in mind when collecting productivity metrics for projects, one should be sure to establish a taxonomy of project types. This will enable to compute domain specific averages making estimation more accurate.

LOC and FP techniques differ in how decomposition is used. Consider a case when LOC is used, it is essential to use decomposition and that too to a fairly detailed level. In order to get a higher level of accuracy, it is necessary to have a high degree of partitioning.

Now considering the case of FP, the usage of decomposition is different. It is required to get the five information domain characteristics, and the complexity adjacent values. Once these are available, and using past data, an estimate can be generated.

Alongside, a project planner estimates a range of values using historical data; these are the optimistic, most likely, and pessimistic sizes for each function. Based on these, an expected value for the estimation variable can be calculated.

Project Estimation - Decomposition techniques - Estimating the software size

In the estimation of software cost and effort, many variables that include human, technical, environmental, political can affect final cost and effort applied to software. It is a complex process. Decomposing the problem and re-characterization it into a set of smaller problems is an approach for software project estimation.

Decomposition approach has two point of views :
- problem decomposition
- process decomposition

Before estimating, estimating the size of the software is very important. The size of the software to be built can be estimated using lines of code which is a direct measure or through function point which is an indirect measure. Estimating software size is a major challenge. Size is the quantifiable outcome of software project.

Approaches to sizing problems are:
- Fuzzy logic sizing: Identify the application, its magnitude and refining the magnitude within original range.
- Function point sizing: Estimates of information domain characteristics are developed.
- Standard component sizing: The number of occurrences of each standard component
is estimated and project data is used to calculate the delivered size per standard component.
- Change sizing: Suppose an existing software is modified in some way. In this approach, the number and type of modifications are estimated.

These approaches were suggested by Putnam and Myers.

A general overview of software estimation techniques...

Few things should be kept in mind while the software project planner begins the project:
- how long will it take?
- how much effort is required?
- how many people are involved?
- what resources are required?
- what kind of risk is involved?
The statement of scope helps the planner develop estimates using one or more techniques that fall into two broad categories:
- decomposition
- empirical modeling.

Decomposition techniques require a delineation of major software functions followed by estimates of either:
- the number of lines of code.
- selected values within the information domain.
- number of use cases.
- number of person months required to implement each function.
- number of person months required for each software engineering activity.

Empirical techniques use empirically derived expressions for effort and time to predict these project quantities. Automated tools can be used to implement a specific empirical model.

By comparing and reconciling estimates derived using different techniques, the planner is more likely to derive an accurate estimate. Software project can never be an exact science but it is a combination of good historical data and systematic techniques that helps in improving estimation accuracy.

What is a process framework? What is the approach of a successful project?

The process framework establishes a skeleton for project planning. It is adopted by allocating a task set that is appropriate to the project. There should be some flexibility given to the software team to select the best process model and engineering tasks suitable for the project.
- For a small project, linear sequential approach can be used.
- If for a project, tight time constraints are applied, RAD model can be used.
- If for a project, deadline is very tight, an incremental approach can be used.

After the selection of the appropriate process model, process framework is adapted to it. The process framework is invariant in nature and it acts as a basis for all software work.Process decomposition starts when the project manager wants to know how can this framework activity be accomplished.

Approach to manage a successful software project are:
- One should start on the right foot.
- Momentum should be maintained.
- Progress should be tracked.
- Decisions should be made smartly.
- Postmortem analysis should be conducted.