CONTEXTUAL KNOWLWDGE REASONING REQUIRES PRECISE BUT FLEXIBLE FORMALISMS IN SUCH A WAY THAT, TOGETHER WHIT THE CAPACITY TO REASON WHIT WELL DEFINED INFORMATION IN THE CONTEX. THREEVALUED MODELS OF KRIPKE ARE PROPOSED AS THE CONTEXT FORMAL SETTING. IS SHOWED HOW THOSE REPRESENTATION KNOWLEDGE FRAMEWORKS ARE ADEQUATED TO ALLOW THE DYNAMIC MANNER IN WICH CONTEXT INFORMATION EVOLVE. OPERATION DEVOTED TO ESPAND OR TO CHANGE CONTEXT ARE DEFINED. IN ADDITION, THE HEURISTICAL ADEQUACY OF SO DEFINED CONTEXTS CAN BE ESTABLISHED THOUGH THE DIRECT CORRESPONDANCE BETWEEN THEM AND THE ANALYTIC TABLEUX DEMOSTRATION METHOD.CONTEXTUAL KNOWLWDGE REASONING REQUIRES PRECISE BUT FLEXIBLE FORMALISMS IN SUCH A WAY THAT, TOGETHER WHIT THE CAPACITY TO REASON WHIT WELL DEFINED INFORMATION IN THE CONTEX. THREEVALUED MODELS OF KRIPKE ARE PROPOSED AS THE CONTEXT FORMAL SETTING. IS SHOWED HOW THOSE REPRESENTATION KNOWLEDGE FRAMEWORKS ARE ADEQUATED TO ALLOW THE DYNAMIC MANNER IN WICH CONTEXT INFORMATION EVOLVE. OPERATION DEVOTED TO ESPAND OR TO CHANGE CONTEXT ARE DEFINED. IN ADDITION, THE HEURISTICAL ADEQUACY OF SO DEFINED CONTEXTS CAN BE ESTABLISHED THOUGH THE DIRECT CORRESPONDANCE BETWEEN THEM AND THE ANALYTIC TABLEUX DEMOSTRATION METHOD.