ABSTRACT
This chapter aims to address the application of multi-criteria methods on discrete variables, which constitute an advanced topic in Operational Research and that have a high potential for application in complex decision-making processes in diverse fields. This chapter presents the use of the ELECTRE I methods as the tool that will allow finding the optimal solution in balancing a group of projects, selecting suppliers or setting a portfolio investment scheme, using financial and non-financial variables. The chapter is structured in two main parts: the first will explain the nature and composition of the ELECTRE methods, especially, in the ELECTRE I class, and the second part will present application examples based on adapted real cases.
