Software Engineering Institute

This column is the ninth in a series about estimating. After this there is only one more column on estimating methods. There is then one further column in this series on the results engineers have obtained by using the PROBE method in practice.  After that, you will know how object-oriented methods can help you make good estimates and plans for your software work. 

If you are new to this series of columns on Estimating with Objects, the first was in the July 1996 Object Currents issue.  The prior columns in this series gave an overview of estimating and defined the steps needed to make size and resource estimates.  If you have not read these earlier columns, you should look at them first to understand the context for this discussion and to see how these various estimating topics relate.  To repeat what I have said in previous columns, the estimating method described here is called PROBE.  If you want to quickly learn more about PROBE, you should read my book A Discipline for Software Engineering, from Addison Wesley.  This book introduces the Personal Software Process (PSP)SM, which is an orderly and defined way for software engineers to do their work.

This month's column continues the discussion of how object-oriented techniques can help you to estimate and plan your work. To make a project plan, you need a resource estimate and, to estimate resources, you need to estimate the size of the product you plan to build. Also, to make good estimates, you need historical data on the sizes and development times for the programs you have previously written. The previous columns described how to gather these data and how to use them to make size and resource estimates. In this column, we describe how to produce a project schedule from these data.  While the steps are not complex, they involve some subtle considerations.  This column reviews the issues involved in making schedules, discusses how to address these issues, and outlines a helpful schedule estimating procedure.