Implementable Technology Specification

Glossary Definition: usage of the term Implementable Technology Specification (ITS) is ambiguous:

• It mostly refers to a specification that describes a method of encoding HL7 messages.
• In some cases it refers to a Transport or more precisely the Messaging Infrastructure Layer. This usage of the term ITS is discouraged. Historically (see MDF99) an ITS was defined as the combination of encoding+transport, whereas nowadays these two layers have been separated.

Background: MDF99

The MDF99 states:

• The [ITS] precisely defines the representation of HMD contents in a specific messaging syntax.
• [Glossary for ITS] "A specification that describes how HL7 messages are sent using a specific Implementation Methodology [A method of Encoding and sending of HL7 Messages. Version 3 implementation technologies will include ER7, object-oriented, and perhaps, EDIFACT]. It includes, but is not limited to, specifications of the method of encoding the messages, rules for the establishment of connections and transmission timing, procedures for dealing with errors.
• [ITSs are] Seperate syntax specifications, descrbing the mechanisms used to encode and transmit the messages in various implementation technologies including [XML, object-oriented, ER7].

MDF99 further states that:

• The ITS defines all aspects of representation of a data type.
• [An ITS] describes how to combine data with the message type in order to create a message instance. This means that a message sent in the format of one [ITS] can be easily transliterated into the format of another.
• Default values can be specified at any level of the information model [...], in the ITS, and even in a particular message instance if the message definition or the ITS provides a construct for rules to set a default dynamically. default values can be overridden. The default value that is closest to implementation has precedence.
• The ITS must defined how to deal with the seeming paradox of an object appearing at two places in the message instance. This would occur [for example] if the same physician were the attanding physician as well as the admitting physician. [..] The ITS specification may call for replication, so that the data that describes the object appears at both places in the message. It may also call for a way to represent the second occurence as a "stub" that contains only enough information to point to the first occurence. [..] This implementation technique is hidden from those who design HMDs.