This paper concerns the integration and extension of ontology to handle KKR and mobile codes for an RFID middleware system which is built based on Application Level Events (ALE) specification proposed by the EPCglobal standard organization. To convert tag data with various types of code systems into Uniform Resource Name (URN) format, we analyzed and integrated code ontology to apply the knowledge of rules for each code. According to the defined rules, we extended the code ontology with classes, instances, properties and relations among them using Web Ontology Language (OWL) which is one of the ontology definition languages. Experimentally, we recognized that KKR and mobile codes could be effectively processed by using the extended knowledge. Copyright © 2012 by International Society of Computers and Their Applications (ISCA).