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. The apparatus consists of a memory, a means for receiving a query sequence coupled to the apparatus, and a data processing system for comparing the query sequence with each of the stored data sequences and retrieving those data sequences which correspond to the query sequence. The data processing system may be structured so as to contain a plurality of processors working in parallel, each of which operating on a different group of stored data sequence symbols so as to decrease the time needed to find the data sequences corresponding to a given query sequence.