Abstract: A memory system and method for the storage and retrieval of sequences of symbols which may be used to represent rules in artificial intelligence systems. The stored data sequence consist of a plurality of symbols, each symbol belonging to one of three classes, constants, variables, or delimiters. Stored data sequences are retrieved by the apparatus of the present invention in response to a query sequence which consists of a plurality of symbols belonging to the same three classes as the symbols comprising the stored data sequences. A stored data sequence is retrieved in response to a given query sequence if the two sequences can be made identical by replacing each variable element appearing in the two sequences by a constant or a combination of constants and delimiters, said combination beginning and ending with a delimiter. Different constants or combinations thereof may be used for each variable element replaced.