HL7 generally refers to messaging standards HL7 V2.x, HL7 V3.x, HL7 V3.x RIM, document standards Clinical Document Architecture (CDA), and application standards Clinical Context Object Workgroup (CCOW). Of these, the HL7 V2.x and V3.x are especially important because information exchanged among systems is defi ned in these. It should be noted that after HL7 V3.x is released, the development of HL7 V2.x is not stopped yet and new versions of HLV2.x are still released, because there is signifi cant difference between HL7 V2.x and HL7 V3.x, and installed base of HL7 2.x is very high.