Importance

Loading Importance Indicators...

Abstract

A machine-implemented process, and apparatus, for performing a set membership test on large sets through the technique of binary hash coding with a known allowable expectation of an error. The present invention does not employ content addressable memory; rather, the present invention performs set membership testing by utilizing a hash function, which produces a randomized plurality of simple address locations within a bulk memory, for each item in the set. A testing for membership comprises employing a logical AND operation upon all values of binary indicators at memory locations addressed by hash values of a test item, to determine whether each and every hash value generated for the test item exactly matches with previously loaded indicators at those address locations in the bulk memory, which in the pereferred embodiment is of the CCD type. The present invention is a machine-implemented process, and employs a known algorithm as part of the overall process. The present invention also essentially comprises synergistic interaction of a hardware item called a 'hash board', and a bulk memory. The hash board generates a large number of hash addresses for any given item, using minimal computation time. The expected error rate is a function of the vocabulary size and the total number of indicators in the bulk memory. The bulk memory allows a low error rate for large vocabularies without exceeding the statistically ideal loading density of 50 percent. The hashing technique, together with its hardware implementation, allows a black box approach to general set membership testing. Information stored in the bulk memory can be said to be encrypted because the randomizing process makes it impossible to retrieve the original set of items. A preferred embodiment of the machine-implemented process, and apparatus is for on-line spelling checking of each word which appears in daily newspaper production, against a selective 20,000-word vocabulary, previously stored as a randomized set of simple bit addresses.

Loading the Abstract Image...

First Claim