Software reuse is essential in improving efficiency and productivity in the software development process. This paper analyses reuse within requirements engineering phase by taking and adapting a standard functional size measurement method, COSMIC FFP. Our proposal attempts to quantify reusability from Object Oriented requirements specifications by identifying potential primitives with a high level of reusability and applying a reuse indicator. These requirements are specified using OO-Method, an automatic software production method based on transformation models. We illustrate the application of our proposal in a Car Rental real system
