Health Level Seven (HL7) is a standard series of predefined logical formats for packaging healthcare data into messages to be transmitted among computer systems.
In contrast to the DICOM standard, which covers the imaging domain, HL7's domain is clinical and administrative data. HL7 is primarily concerned with the data content and interrelationship of messages and with communicating certain application-level error conditions. HL7 is not commercial software or data transfer package, but instead is a defined set of rules for sending simple text characters in groups that represent patient identifiers, clinician identifiers, laboratory test information, test results, and other clinical and administrative data.
HL7 corresponds to the conceptual definition of an application-to-application interface placed in the seventh layer of the OSI model. HL7 is one of several American National Standards Institute (ANSI) -accredited Standards Developing Organizations (SDOs) operating in the healthcare arena.
HL7 allows communication between separate and different types of information systems. These systems may range from small, highly specialized laboratory analyzers to large inter-enterprise information repositories. Any system that conforms to HL7 is expected to comply with the rules that are laid out in the standard. These rules cover two broad areas: the formation of messages (what elements constitute a message and how these elements are put together), and the communication of messages (how systems send messages back and forth, and how they verify the receipt and custody of the data in the messages).
The United States home page for HL7 is http://www.hl7.org