1. A knowledge system to determine a machine configuration of a given type from a requested machine configuration, each machine configuration having a record including a plurality of parameters, taken from a given family of parameters, and a value for each of said plurality of parameters, the knowledge system comprising: an expert system to process the record of the requested machine configuration to determine therefrom a machine configuration of the given type; a complementary database storing a plurality of records of machine configurations of the given type, all of the values for each one of the parameters of the records stored in the complementary database forming a value set associated with said one parameter; search means to search the complementary database for a record identical to the record of the requested machine configuration, and to indicate to a requestor that the requested machine configuration is of the given type if a record identical to the record of the requested machine configuration is found in the complementary database, and including means to search all of the value sets associated with the parameters of the record of the requested machine configuration, one value set at a time, for all of the values in each value set identical to the value of the associated parameter of the record of the requested machine configuration; and input means to receive from the requestor the record of the requested machine configuration, and to transmit the record thereof to the search means.