Implementable Technology Specification

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

• Generally an ITS is a specification that describes a method of encoding HL7 artefacts. The ITS specifies how abstract models should be transformed into on-the-wire things (e.g. a string, or an object) that can be transmitted.
• In some cases the term ITS refers to a specification for rules for the establishment of connections and transmission timing and procedures for dealing with errors. In this sense of the meaning it equals 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.

Workitem for ITS SIG

It is a work item for the ITS SIG to clarify this entry in the glossary

• Entry in the NE2006 normative edition (core glossary):
• Implementation technology: A technology selected for use in encoding and sending HL7 messages. For example, XML is being used as an implementation technology for Version 3.
• Implementation Technology Specification: A specification that describes how HL7 messages are sent using a specific implementation technology . It includes, but is not limited to, specifications of the method of encoding the messages, rules for the establishment of connections and transmission timing and procedures for dealing with errors.

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 define 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.