Before revision:  This didactic text provides a brief review of some of the approaches that have been used to characterize complexity, and also suggests a possible definition of complexity based on the cost assigned to mapping the entity of interest, as well as on the  cost of the error implied by its respective reconstruction .
After revision:  This didactic text provides a brief review of some of the main approaches to complexity; and (ii) to suggest a cost-based approach that, to a great extent, can be understood as an integration of the cost of the error implied by its respective reconstruction .