Contexts
A context is constituted by a consistent environment (set of assumptions) and by all the nodes which are derivable from these assumptions.
A context may be seen as a complete model of the world, including all known information about it, a specific set of assumptions, and all the information derivable from them.
A context is characterized by an environment. If we have n possible assumptions, there are potentially 2 possible contexts. Some of them can be nogood.