This report introduces a JAVA library whose objective is to provide tools for solving some network optimization problems and that may be used to write prototype software. We describe here the first step of the development which concerns algorithmic graph problems. This open source library named MASCOPT includes an implementation of a generic model of graph. This library has been designed with an object-oriented model and aims to be user friendly rather than focusing on speed of execution. We show how the model can be extended and dedicated to a user application by using simple object mechanism. We also present a basic description of the MASCOPT functionalities so that developers, who are familiar with objects, can use effectively for their own experimentations.