Abstract
Software Cost Estimation (SCE) continues to be a weak link in software project management. It is the responsibility of the project manager to make accurate estimations of effort and cost. This is particularly true for projects subject to competitive bidding where a bid too high compared with competitors would result in loosing the contract or a bid too low could result in a loss to the organization. From an estimate, the management often decides whether to proceed with the project. Industry has a need for accurate estimates of effort and size at a very early stage in a project. However, when software cost estimates are done early in the software development process the estimate can be based on wrong or incomplete requirements. Software cost estimate process is the set of techniques and procedures that organizations use to arrive at an estimate.Why SCE is difficult and error prone?- Software cost estimation requires a significant amount of effort to perform it correctly.- SCE is often done hurriedly, without an appreciation for the effort required.- You need experience at developing estimates, especially for large projects.- Human bias i.e. an Estimator is likely to consider how long a certain portion of the system would take, and then to merely extrapolate this estimate to the rest of the system, ignoring the non-linear aspects of software development.- Costs and schedules are often pre-determined by an outside source.- An in-depth analysis of the software development process w as no t undertaken or in many cases, is not fully understood- There is a general lack of acceptance that developing software is an expensive endeavor.The causes of poor and inaccurate estimation are: (a) imprecise and drifting requirements. (b) New software projects are nearly always different form the last. (c) Software practitioners don't collect enough information about past projects. (d) Estimates are forced to match the resources available.The software estimation process discussed in this paper describes the steps required for establishing initial software Life Cycle Cost estimates and then tracking and refining those estimates throughout the life of the project. Establishment of this process early in the life cycle will result in greater accuracy and credibility of estimates and a clearer understanding of the factors that influence software development costs.
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Index Terms
- Estimating software projects
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Reviews
Robert C. Larrabee
Software cost estimation (SCE) is addressed in this paper. The SCE field has substantially matured since the publication of Software Engineering Economics in 1981 [1]. In the past 21 years, we have seen the field grow beyond the original top-down parametric estimation methods such as constructive cost modeling (COCOMO), PRICE, and system evaluation and estimation of resources (SEER). Other SCE methodologies include bottom-up (namely, engineering estimation) and expert methodologies, including collaborative processes such as the wideband Delphi technique and various adaptations from operations research and the decision sciences. The authors’ experiences at Infosys Calcutta are also addressed. This Bangalore, India branch of Infosys was one of the original Capability Maturity Model for Software (SW-CMM) level 5 companies, so they have presumably collected ample past performance data at the corporate level. The authors provide a taxonomy of SCE and a data flow and process estimation diagram that looks very much like CMM. It references the organization software process database, a CMM level 3 creation. The authors parse SCE into parametric and heuristic branches, but still cover the discipline as it exists today. They give a particularly nice exposition of Boehm’s COCOMO II, and the meaning of all of the parametric variables. I found their Delphi estimation form particularly useful. Apparently, Infosys has refined this technique, and this form represents the culmination of their efforts. Although it adds few new insights to SCE, the paper is informative. I was surprised not to see a mention of Boehm’s latest book [2], which became available in 2000. To conclude, this paper is a concise survey of software cost estimation. Online Computing Reviews Service
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