Abstract
Reactive systems are often described by interconnecting sub-components along architectural connectors defining communication policies. Generally, such global systems may exhibit properties, often called "emergent properties", that cannot be anticipated just from a complete knowledge of components. These emergent properties are twofold: (1) the global system can question properties attached to components; (2) some global properties cannot be inferred only from a complete knowledge of components, but for being inferred, need the knowledge of cooperation mechanisms between components.