1. A computer-readable medium encoded with an inferring system for a vehicle or an occupant of the vehicle making an inference for a situation by using a rule expressed in an If-Then form including a conditional clause and a dependent clause, the inferring system comprising: means for storing a rule group the rule group comprised of a plurality of rules; the rules individually comprised of the conditional clause and the dependant clause; the conditional clause having a linguistic or numerical condition relating to one or more of a plurality of preset situation attributes; the preset situation attributes relative to the conditional clause in the rules including attributes of situations, each situation being associated with at least one of the vehicle and the occupant of the vehicle, the dependant clause having a scoring vector; the scoring vector comprised of a plurality of dimensions being a plurality of preset demand attributes, each dimension having a component represented by a numerical value being a degree of a demand for each of the plurality of preset demand attributes; the demand attributes relative to the dependent clause in the rules including attributes of demands, each demand being associated with the occupant of the vehicle; means for obtaining situation data for recognizing the situation, determining whether a conditional clause of the rule is sufficient or not based on the obtained situation data, and extracting a scoring vector as a component represented as a numerical value of the dependant clause of each of the rules determined to have sufficient conditional clauses; means for generating a demand vector; the demand vector having dimensions being the demand attributes in a state generally recognized from the situation data by performing a process of cumulating the scoring vectors extracted by the obtaining means, each dimension having a component represented by a numerical value being a degree of a demand for each demand attribute; and means for generating an inference result based on the demand vector generated by the generating means, wherein the inference result is derived by choosing the demand attributes having the highest degree of demand; and means for displaying the inference result as a selection key on an interactive display unit.