2. A method as defined in claim 1 wherein the size of said data base is defined by a number of bytes and wherein said keywords comprise substantially all words contained in each record of said data base.
2. A method as defined in claim 1 wherein the size of said data base is defined by a number of bytes and wherein said keywords comprise substantially all words contained in each record of said data base. 4. A method as defined in claim 2 wherein said step of transforming each said vector comprises transforming a binary representation of said vector to a bit string in which the number of bits is reduced, on the average, to not more than approximately one-fifth the number of bits contained in said binary representation of said vector.