The is-a relationship among actors has been introduced in the i* framework since its definition. However, its effect at the level of intentional elements and dependencies is not always clear. The main goal of this thesis is presenting a complete and non-ambiguous definition of inheritance for the i* framework. With this aim, it is necessary to define the modelling operations that make use of inheritance, explain how inheritance affects i* treatments and properties, and how the inherited elements can be represented graphically