A method and system for storing and retrieving compressed data such as ZIP+4 add-on's for postal addresses, compresses source data records by defining a group of attributes which represent the characteristics of source data records and the relationships between source data records and between elements of source data records, each attribute having an associated predetermined set of rules which define specifically the characteristics or relationships represented by that attribute. Source data records are compressed by assigning to a record a tuple of attribute values and a set of modifier values. The attribute values each designate a particular one of the set of rules for its corresponding attribute, and the modifier values comprise values which are used by the rules to express the information content of the source data record. The compressed data records are stored in a memory having a hierarchical data organization along with memory address elements for accessing compressed data records. The memory is controlled by a microprocessor which accesses compressed data records, decodes the identifier and modifier fields of the record, and decompresses the record in accordance with the rules specified by the attribute values.