Software parametric models

A parametric model is a set of related mathematical equations in which alternative scenarios are defined by changing the assumed values of a set of fixed coefficients (parameters). Software project managers use software parametric models or parametric estimation tool to produce estimates of a project's duration, staffing and cost.

The early 1980’s saw the emergence of several software estimation models. These included the refinement of earlier models, such as PRICE S and SLIM, and the development of new models, such as SPQR, Checkpoint, ESTIMACS, SEER or COCOMO and its commercial implementations PCOC, GECOMO, COSTAR and Before You Leap.

One of the earliest software parametric models is Software LIfecycle Management (SLIM) by QSM, founded in 1978 by Lawrence PUTNAM, Sr. SLIM is based on the Putnam model and backed by a database of over 6300 completed projects from all types of industries all over the world, database refreshed with 200 to 400 validated projects a year.

TruePlanning by PRICE Systems introduces a unifying framework to enable the integration of multiple cost models. These cost estimation models support projects involved with application (software) development, IT asset management, and hardware development. TruePlanning supports 3rd party cost models such as COCOMO II. PRICE Systems is truly the earliest developer of parametric cost estimation in its more than 30 year history.

SEER by GALORATH features a sophisticated user interface to track and, therefore, reduce risk by making timely, accurate and insightful decisions about the imposing, interdependent and often immeasurable costs, schedules and staffing variables.

COSTAR is a commercial implementation by SOFTSTAR systems of COCOMO, featuring trade-offs and what-if analysis, plus user definable cost drivers, to arrive at the optimal project plan.

In general, the advantages of these models are that they are objective, repeatable, calibrated and easy to use. Calibration to previous experience may though be a disadvantage when the nature of the project changes.

These models were highly effective for the waterfall-model, build-from-scratch software projects of the 1980’s and marked the early achievements of parametrics. As systems became more complex and new languages came to light, different software parametric models emerged which involved new cost estimating relationships, risk analyzers, software sizing, nonlinear software reuse or personnel continuity, to cite a few.