Software size estimation is an important task for a successful software development. There are a number of systematic methods to estimate the size of software systems, in which the function point analysis has achieved wide acceptance. Among various function point analysis methods, this paper is a relatively new approach and its application is also relatively easier than most methods. The estimation is based on requirement analysis artifacts such as use cases, sequence diagrams or class diagrams. However, these artifacts are often insufficient to verify the precision of the estimation methods, let alone adjust these methods to different domains and organizations.