Product Vocabulary

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Product Brief - HL7 Vocabulary Specifications

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Product Name - Vocabulary


  • HL7 Concept Domains
  • HL7-supported Code Systems
  • HL7 Value Sets

Standard Category

  • Health Information Modeling Standards

Integration Paradigm

  • Foundation


Consensus approval within HL7 by established RIM and Vocabulary Harmonization process. Any Code System, Concept Domain or Value Set that is balloted as part of another HL7 standard (such as the RIM) becomes a normative artifact.


Releases are posted throughout the year as the Harmonization process proceeds. These are posted in a Design Repository (rimRepos) release on Gforge.


Modern health care communications and data storage makes heavy use of encoded information. In HL7, this is referred to as vocabulary. The HL7 standards define several different type of objects that implement various characteristics of vocabulary. Whereas other elements of the HL7 standards are primarily concerned with structure, vocabulary deals with content.


Consistent with the Version 3 philosophy of successively constraining an abstract information model, the least constrained category in vocabulary is a Concept Domain. [Revise and link Master Glossary]: An HL7 Concept Domain is a named category of like concepts (semantic type) that will be bound to one or more coded elements. Concept Domains exist because we want to constrain the intent of a coded element while deferring the association of the element to a specific coded terminology until later in the standards development or implementation process. Thus, Concept Domains are independent of any specific vocabulary or code system.

The categorization of Concept Domains is hierarchical allowing for further constraint on the breadth of the semantic category covered by the Concept Domain. Such constrained domains are known as “sub-domains”. Sub-domains allow for further specialization (constraint) on the intended values for a domain.

A list of intended values for a concept domain or sub-domain is referred to as a value set. A value set consists of one or more coded concepts. These are the possible concept codes that can be carried in an HL7 Version 3 message in a coded data type . When a value set is associated with given concept domain or sub-domain, this is called "binding". Different value sets can be associated with the same concept domain in different circumstance.

A concept code is only unique within a particular context. As an example, "M" may stand for male in one context and married in a second. The context in which a concept is defined is called a code system. Many code systems already exist in the medical domain, such as ICD-9, SNOMED-CT, etc. Whenever possible, HL7 reuses existing concept codes rather than developing their own.

At the point that message designers and implementers decide on the specific terminology to represent the information payload of a coded element, a value set is bound to the concept domain that was the previous constraint for the coded element, and that value set is asserted as the new constraint for the coded element.

The HL7-defined vocabulary tables that have been developed for coded class attributes are stored in the HL7 repository, from which a number of views have been extracted to produce the HL7 Vocabulary Listings for the HL7 Reference Information Model (RIM). The views are presented in table format and include the HL7 Concept Domains, Code Systems (including, HL7-maintained systems and external systems referenced by HL7), HL7-defined Value Sets, and a Cross Reference between Concept Domains and Coded Attributes.

The Concept Domain name and the associated extensibility qualifier for each coded attribute in the RIM are specified in the RIM narrative. This specification occurs as the first line of the attribute's description in the following format: Concept Domain: "MyConceptDomain" (CWE)

There is a link between the concept domain name in the RIM listing and its entry in the HL7 Concept Domain table in this listing.

Business Case (Intended Use, Customers)

The vocabulary specifications, along with the RIM and Data Types form the foundation for all information modeling within HL7. The models derived from these serve as documents, data for services, and messages. As such, they are "part" of every HL7 Version 3 standard and have the same "customers" as do the standards defined from them.


The essence of Version 3 is the establishment of an information modeling foundation that is:

  • relatively stable,
  • able to support the representation of all concepts in the HL7 domain of interest, and
  • is technology-neutral in order to allow implementation in a variety of environments as the users technology evolves.

The Vocabulary, RIM and Data types provide this foundation.

Implementations/ Case Studies (Actual Users)

  • Every Actual User of another V3 Product - CDA, Messaging or Services


Work Groups



Certification Available
  • none


Relationship to/ Dependencies on, other standards

Links to current projects in development

  • none at this time