24. An inference engine for use in an expert system controlled by a matrix of learning coefficients having a matrix value for each combination of one from a set of resultant variables and one from a set of primary variables, said set of primary variables at least including a set of input variables, said inference engine comprising: means for calculating a likely value of a resultant variable from known values of primary variables and the matrix values associated with said resultant variable; means for determining whether said likely value is a final determination, said likely value being a final determination when said likely value would be unchanged regardless of the value of the primary variables whose values are not known; and means for determinig an input variable which will contribute to making a final determination of a resultant variable whose value has not been finally determined.
27. The inference engine of claim 24 wherein said means for calculating a likely value of a resultant variable is performed by summing the products formed by multiplying each of said known values of primary variables by the matrix value in the matrix of learning coefficients associated with both said resultant variable and the primary variable corresponding to the known value.