Abstract
The aim of the article is to present elements to build a conventionnalist micro-economy. The economy of conventions tends to integrate conventions (or rules of behaviour) as basic economic units. A definition of the concept of convention is first given, and the link between it and the notion of the individual "liberty" is compatible with common rules. To take them into account, it is necessary to understand the dynamics of economics. Conventions are systems of information: secondly, the consequences of this assumption are explained. This opens new perspectives in micro-economics, based on the nature of "conviction" of individuals and lock-in effects involved.