Barry Boehm Quotes

The spiral model presented in this article is one candidate for improving the software process model situation. The major distinguishing feature of the spiral model is that it creates a risk-driven approach to the software process rather than a primarily document-driven or code-driven process. It incorporates many of the strengths of other models and resolves many of their difficulties.

Most post-mortems of these software disaster projects have indicated that their problems would have been avoided or strongly reduced if there had been an explicit early concern with identifying and resolving their high-risk elements. Frequently, these projects were swept along by a tide of optimistic enthusiasm during their early phases, which caused them to miss some clear signals of high risk issues which proved to be the project's downfall later.
Enthusiasm for new software capabilities is a good thing. But it needs to be tempered with a concern for early identification and resolution of a project's high-risk elements, so that people can get these resolved early and then focus their enthusiasm and energy on the positive aspects of their software product.

Economic principles underlie the overall structure of the software lifecycle, and its primary refinements of prototyping, incremental development, and advancemanship. The primary economic driver of the life-cycle structure is the significantly increasing cost of making a software change or fixing a software problem, as a function of the phase in which the change or fix is made.

The stagewise and waterfall models. As early as 1956, experience on large software systems such as the Semi-Automated Ground Environment (SAGE) had led to the recognition of these problems and to the development of a stagewise model to address them.

If we look at the discipline of software engineering, we see that the microeconomics branch of economics deals more with the types of decisions we need to make as software engineers or managers.

Agile development methodologies promise higher customer satisfaction, lower defect rates, faster development times and a solution to rapidly changing requirements. Plan-driven approaches promise predictability, stability, and high assurance. However, both approaches have shortcomings that, if left unaddressed, can lead to project failure. The challenge is to balance the two approaches to take advantage of their strengths and compensate for their weaknesses.

Stop the life cycle-I want to get off!

Poor management can increase software costs more rapidly than any other factor. Particularly on large projects, each of the following mismanagement actions has often been responsible for doubling software development costs.

Success in all types of organization depends increasingly on the development of customized software solutions, yet more than half of software projects now in the works will exceed both their schedules and their budgets by more than 50%.

Like many fields in their early stages, the software field has had its share of project disasters: the software equivalents of Beauvais Cathedral, the S.S. Titanic, and the "Galloping Gertie" Tacoma Narrows Bridge. The frequency of these disaster projects is a serious concern: a recent survey of 600 firms indicated that 35% of them had at least one "runaway' software project.

The dictionary defines "economics" as "a social science concerned chiefly with description and analysis of the production, distribution, and consumption of goods and services." Here is another definition of economics which I think is more helpful in explaining how economics relates to software engineering.

What we see in both software development and military operations is a tendency for the pendulum to swing back and forth between extremes. Yet in most cases, we need a balance between armor and discipline and between mobility and agility. Actually, though, I would say that the leaders in both the agile and plan-driven camps occupy various places in the responsible middle. It’s only the over-enthusiastic followers who overinterpret “discipline” and “agility” to unhealthy degrees.

If a project has not achieved a system architecture, including its rationale, the project should not proceed to full-scale system development. Specifying the architecture as a deliverable enables its use throughout the development and maintenance process.

The Code-and-Fix Model. The basic model used in the earliest days of software development contained two steps:

Throughout the software life cycle, there are many decision situations involving limited resources in which software engineering economics techniques provide useful assistance.