Management of the software development process requires a thorough understanding of the environment in which development takes place. Ability to estimate, plan, and manage resource consumption is limited by the central problem of determining the size of system specifications. To address this issue, a general strategy for measurement and evaluation of system development environments needs to be established. This article presents a research model that will help managers and researchers understand and establish the linkages between units of systems requirements specification, design, and source code. Initial validation of the model was performed by reverse engineering systems written in a fourth generation language from source code to design metrics. Results indicate that the model may provide reliable measures of system size in terms of both design metrics and lines of code.