14. The computer system according to claim 12 , wherein the calculator is arranged to apply a scaling factor to the activation attribute values so that the sum of the activation values of the context entities is substantially a constant.
12. The computer system according to claim 11 , wherein the calculator is arranged, in a first cycle, to assign a preset activation value to the at least one context entity and, in a second and any subsequent cycle, to recalculate the activation attribute value by taking into account the sum of the activation attribute values of an entity related to the at least one context entity.