'The report proposes a new graphical input specification language g-Promela for SPIN model checker. Basic features of PROMELA language are defined using the formal syntax of graphical elements as an extension of labeled transition systems. The labels are specified with valid PROMELA statements. To facilitate the handling of g-Promela specifications, we have sketched the design of the Graphical Promela Interface(GPI) toolset, which is built upon the existing UPPAAL GUI. The graphical models are then translated to textual PROMELA to verify temporal properties using SPIN engine in the background. The translation is automated by building a parser which is part of the adapter tool built between the User Interface and SPIN engine. As a prime example, peterson’s Mutual Exclusion Algorithm is modeled and verified.'