Requirements-Shared Reference Model

To ensure consistent interoperability, HL7 version 3 makes use of a shared reference model that defines the sole set of constructs that may be used when constructing HL7 v3 standards. The reference model is made up of three portions:

• A static information model - the Reference Information Model (RIM)
• A datatypes model - the Universal Datatypes
• A terminology model - the HL7 Vocabulary

Requirement	For semantic interoperability, some data elements will need to be constrained to be drawn from a constrained set of values where distinct concepts are each represented by a single value.
Rationale	When searching or attempting to perform decision logic based on data in an instance, it's essential that the value used to represent a given concept in the system initiating the communication can be recognized as meaning that same concept in the system receiving the communication.
Methodology	Coded data: Most data elements in HL7 v3 standards that are used to convey "concepts" (rather than free text, numbers, booleans and other non-concept data) are assigned datatypes for Coded information. The specification elements that reference these coded datatypes use Terminology Bindings to reference the set of allowed concepts and values for those concepts. Where possibles, HL7 leverages shared concept definitions maintained by other organizations, though sometimes it also defines its own concepts. These concepts and their representations are organized together into Code Systems. To support the set of terminologies and terminology artifacts necessary to create those bindings, HL7 provides a Terminology Model

TODO: RIM Model, Datatypes Model