Step Eight: Generate A Project Plan
The process of generating a project plan includes taking the estimate and allocating the cost and schedule to a function and task-oriented work breakdown structure. Models such as SEER Client for Microsoft perform this function automatically. The eight major software development phases
are: (1) concept, (2) acquisition, (3) requirements, (4) design, (5) code and unit test, (6) integration, (7) acceptance, and (8) post deployment.
Determining Costs from Effort Estimates
At this point in the estimation process, you should have a reasonably accurate projection of your project’s size and required effort, that is, an estimate of the number of person-hours by component and a sum of these projections, and you can now begin to price the estimate. As software estimation models generally account only for costs related directly to development, you may need to translate the required effort to a cost and finalize the estimate by adding in essential nonlabor costs. You can do so by answering the following questions:
What types of individuals do I need and when do I need them?
Identify the specific personnel requirements by task area (direct software management, software systems engineering, design, programming, configuration management, quality assurance, etc.). Develop a strawman schedule from the work breakdown structure or a staffing plan such as the one produced by SEER-SEM.
How experienced do they have to be? Assign specific staff levels to the task requirements and identify the level of experience required to satisfy the task. Some of the automated cost models will identify the tasks and develop a task-based schedule, which will minimize but not eliminate all of the work required to produce the software development plan.
Ten-step Project Estimation Process
Software Estimation Concepts
Many project managers and project management offices have unrealistic expectations about estimates. The definition of the verb estimate is to produce a statement of the approximate value of some quantity. Estimates are based upon incomplete, imperfect knowledge and assumptions about the future. For these reasons, many estimates of software costs tend to be too low due to omissions of important product functions and project activities. Most importantly, however, all estimates have uncertainty. There is no such thing as a precise, single-value estimate. Managers should always ask how large the uncertainty of an estimate is! A manager can use the size of this uncertainty in conjunction with other factors such as perceived risks, funding constraints, and business objectives to make decisions about a project.
How can projects address the uncertainty of poor estimates? How can the risks associated with initial estimates be identified, managed, and controlled? The answer is straightforward: by defining, establishing, planning, and applying a consistent, repeatable, and effective estimation process.
A software estimation process that is integrated with the software development process can help projects establish realistic and credible plans to implement the project requirements and satisfy commitments. It also can support other management activities by providing accurate and timely planning information. Realistic plans will also describe how the resources that are required to undertake the initiative in accordance with the schedule will be secured. The planning process, as critical as it is, is difficult and takes time to perform correctly. Managers often truncate the planning process by using “easily available” information that is often inadequate; by employing whoever has the time, even if those individuals are not qualified to perform the estimate; and by using only one estimation method to save time.
Successful software engineering requires the application of engineering principles guided by informed management. The principles must them-selves be rooted in sound theory. While it is tempting to search for miracles and panaceas, it is unlikely that they will appear. The best course of action is to stick to age-old engineering principles. There simply are no silver bullets.
Cost estimates are projections of required effort, time, and staffing levels. Because all estimates, particularly those made at the beginning of a project, are based on assumptions, they should be considered probabilistic. Cost estimates in particular should provide a range with an indication of accuracy, i.e., least, probable, and most, with the least and most values representing the upper and lower bounds of the projected cost.
Project Estimation Process
Ideally an estimate should be produced using the ten-step process.
During October we will cover each step on this blog.
