The present invention relates to a system and computer-readable medium for storing a plurality of multi-field classification rules in a computer system. Each multi-field classification rule includes a rule specification that itself includes a plurality of fields and a plurality of field definitions corresponding to the fields. The method of the present invention includes providing a virtual rule table, where the table stores a plurality of field definitions, and for each of the plurality of multi-field classification rules, compressing the rule specification by replacing at least one field definition with an associated index into the virtual rule table. The method also includes storing each of the compressed rule specifications and the virtual rule table in a shared segment of memory.