HL7(Health Level 7) Intro.....

HL7 isn’t a language per say but rather a set of standards that dictate the format in whicelectronic information is exchanged between otherwise disassociated healthcare systems. 

•   HL7 is standard for the interchange of healthcare data. 
•   A set of message-based transactions between healthcare applications. 
•  HL7 message protocol supports unsolicited messages as well as solicited messages. 
•  HL7 encoding rules produce human-readable variable length delimited ASCII messages. 
•  A domain-specific, common protocol for the exchange of health care information.

       The name "Health Level-7" is a reference to the seventh layer of the ISO OSI Reference model also known as the application layer. The name indicates that HL7 focuses on application layer protocols for the health care domain, independent of lower layers. HL7 effectively considers all lower layers merely as tools.