Overview

Each concept has a concept definition.

A concept definition is a set of one or more axioms that partially or sufficiently specify the meaning of a SNOMED CT concept.

Notes

Concept definitions are represented in two ways in SNOMED CT release files:
- As a stated view represented by axioms that conform to the OWL Functional Syntax distributed in the OWL Expression Reference Set file.
- As an inferred view represented by defining relationships that are distributed in the relationship file. The inferred view is generated by applying description logic classification to the stated view.
Concept definitions include two distinct elements
- Axioms that assert that a concept is a subtype of one or more other concepts. In the inferred view these are represented as subtype relationships.
- Axioms that assert characteristics of a concept that distinguish it from its supertypes. In the inferred view these are represented as attribute relationships.

Requirements and Options

Table 4.4-1 describes several distinct types of access to concept definitions and the client application functionalities that each of these access types supports.

General purpose terminology services that are able to access subtype relationships relationships can be used to meet a limited set of SNOMED CT use cases. However, SNOMED CT terminology services should also provide access to the inferred view of concept definitions.

Advanced SNOMED CT terminology services require the ability to access and interpret the axioms that represent the stated view of concept definitions. They should also enable description logic classification either as a built in service or via an interface to separate classifier. Services that support classification provide added value for data retrieval and analysis by enabling post-coordinated expressions to be classified and appropriately located in the subtype hierarchy.

The required services listed in Table 4.4-2 omit services that only require access to subtype relationships, as these are described in 4.5 Get and Test Concept Subtypes and Supertypes.

Table 4.4-1: Practical Requirements for Access to Concept Definitions

Terminology Service Access to Definitions	Client Application Functionality Supported
Access to subtype relationships: From subtype child to supertype parent From supertype parent to subtype child	Display subtype hierarchy A subtype hierarchy is a classification hierarchy in which each node is connected to its supertypes. Notes Subtype classification allows aggregation of information based on a hierarchy of types.
Access to the transitive closure of subtype relationships: From subtype descendant to supertype ancestor From supertype ancestor to subtype descendant	Testing subsumption between concepts A subsumption test is a test to determine if a specified candidate concept or expression is a subtype descendant of another specified concept or expression.
Access to the complete inferred view of concept definitions, including subtype relationships and attribute relationships	Display of inferred concept definition The inferred view is a representation of concept definitions that is logically derived by applying a description logic classifier to the stated view. Postcoordinated expression creation A subsumption test is a test to determine if a specified candidate concept or expression is a subtype descendant of another specified concept or expression. Expression constraint and query creation An expression constraint is A computable rule that is used to define a set of clinical meanings.
Access to the complete stated view of concept definitions, as OWL axioms	Display of stated concept definition The stated view is a representation of concept definitions consisting only of assertions made or revised by SNOMED CT authors. Terminology authoring A SNOMED CT authoring is the process of creating or editing SNOMED CT concepts, concept definitions and descriptions. Terminology classification A Description logic classification is a process that generates a set of logically consistent inferences by applying description logic rules to the stated view of concept definitions. Expression classification Applying description logic to classify an expression to enable appropriate subsumption testing when reporting records that include postcoordinated expressions

Table 4.4-2: Services Required¹

Service Name and Status	Input	Output
Get inferred necessary normal form definition of a concept ² REQUIRED	Edition and version A concept identifier Optional: Language/dialect³	The inferred definition of the specified concept represented in one of the following ways: A SNOMED CT compositional grammar expression⁴ A data object representing the data in all active rows in the snapshot view of the relationship file in which the sourceId column matches the specified conceptId In either case, the concept identifiers in the definition may optionally be supplemented the preferred term or fully specified name in a specified language or dialect
Get stated definition of a concept ADVANCED	Edition and version A concept identifier Optional: Language/dialect³	The stated definition of the concept represented in one of the following ways: As a set of one or more OWL axioms represented using the OWL Functional Syntax or another specified OWL syntax A SNOMED CT compositional grammar expression In either case, the concept identifiers in the definition may optionally be supplemented the preferred term or fully specified name in a specified language or dialect

Interdependencies

Required By

Depends On

- 4.1 Select Edition and Version
- 4.2 Get a Concept, Description or Relationship

Service Examples

The Snowstorm and FHIR examples are presented in plain text and URL encoded versions. Always use the "Encoded URL" when testing the example service requests. The plain text version is included to aid readability but using this version in a service request may result in errors. These errors result from characters that have to be encoded as they are not permitted in a URL (see IETF RFC1738).

Table 4.4-3: Snowstorm API

Service Name

API Call⁵

Result

Get the inferred necessary normal form definition of a concept

GET [snowstorm]/[branch]/concepts/[conceptId]/normal-form?includeTerms=[true|false]

for example

GET [snowstorm]/MAIN/2020-01-31/concepts/6025007/normal-form?includeTerms=true

Encoded URL

GET [snowstorm]/MAIN%2F2020-01-31/concepts/6025007/normal-form?includeTerms=true

or without including the terms

GET [snowstorm]/MAIN/2020-01-31/concepts/6025007/normal-form

Encoded URL

GET [snowstorm]/MAIN%2F2020-01-31/concepts/6025007/normal-form

Returns a JSON data object containing a compositional grammar expression representing the inferred definition of the concept.

If the optional includeTerms parameter is set to true the expression includes the fully specified names of each concept referenced in the expression. Otherwise only the expression only includes the concept identifiers.

Get the stated definition of a concept

GET [snowstorm]/MAIN%2F2020-01-31/members?referenceSet=733073007&referencedComponentId=[conceptId]

for example

GET [snowstorm]/MAIN%2F2020-01-31/members?referenceSet=733073007&referencedComponentId=6025007

Encoded URL

GET [snowstorm]/MAIN%2F2020-01-31/members?referenceSet=733073007&amp;referencedComponentId=6025007

or as example of a concept defined by more than one axiom

GET [snowstorm]/MAIN%2F2020-01-31/members?referenceSet=733073007&referencedComponentId=473011001

Encoded URL

GET [snowstorm]/MAIN%2F2020-01-31/members?referenceSet=733073007&amp;referencedComponentId=473011001

This service returns a JSON representation of one or more members of in the OWL expression reference set that together represent the stated definition of the identified concept. Each of these reference set members contains an axiom, represented using OWL Functional Syntax, in the additionalFields.owlExpression property string.

Table 4.4-4: FHIR API

Service Name

API Call⁶

Result

Get the inferred necessary normal form definition of a concept

[fhir]/CodeSystem/$lookup?system=http://snomed.info/sct&code=[conceptId]&property=normalForm&_format=json

for example

GET [fhir]/CodeSystem/$lookup?system=http://snomed.info/sct&code=6025007&property=normalForm&_format=json

Returns a JSON representation of information containing the definition of the concept.

The data returned includes the necessary inferred, normal form definition of the concept represented as a compositional grammar expression.

Get the stated definition of a concept

N/A

This service is not supported by the FHIR terminology services API

Table 4.4-5: MySQL Example Database

Service Name

SQL Query ⁷

Result

Get the inferred necessary normal form definition of a concept

-- Get inferred defining relationships
SELECT typeId,destinationId,group 
FROM snap_relationship
  WHERE AND active=1 AND sourceId=[conceptId]
  AND characteristicType=900000000000011006;

for example

-- Get inferred defining relationships
SELECT typeId,destinationId,group 
FROM snap_relationship
  WHERE active=1 AND characteristicType=900000000000011006
  AND sourceId=6025007;

or including terms

-- Get inferred defining relationships with terms
SELECT
  CONCAT(typeId,"|",typeTerm,"|=",
  destinationId,"|",destinationTerm,"|") 'value',
  relationshipGroup 'group'
FROM snap_rel_def_fsn
  WHERE sourceId=6025007;

Returns the set of rows each containing one defining relationship with its associated relationship group number.

Get the stated definition of a concept

-- Get stated defining axioms
SELECT owlExpression 
FROM snap_refset_owlexpression
  WHERE active=1 AND refsetId=733073007
  AND referencedComponentId=[conceptId]
  ORDER BY owlExpression;

for example

-- Get stated defining axioms
SELECT owlExpression 
FROM snap_refset_owlexpression
  WHERE active=1 AND refsetId=733073007
  AND referencedComponentId=6025007
  ORDER BY owlExpression;

or as example of a concept defined by more than one axiom

-- Get stated defining axioms
SELECT owlExpression 
FROM snap_refset_owlexpression
  WHERE active=1 AND refsetId=733073007
  AND referencedComponentId=473011001
  ORDER BY owlExpression;

Returns the set of rows each containing one OWL axiom.

The sort order used in this query ensures that class axioms appear before any GCI axioms ⁷

Footnotes

1

Table 4.4-2 only includes services that access the stated or inferred view of a complete concept definition. Services that access subtypes and supertypes of concepts are described in 4.5 Get and Test Concept Subtypes and Supertypes.

2

The necessary formal form refers to the logical form in which inferred concept definitions are represented in the relationships file. This form is unable to represent some of the axioms present in the enhanced description logic supported by OWL expressions in the stated view of some concept definitions.

3

Language and/or dialect should be specified if the service returns terms associated with referenced concepts.

4

For details of SNOMED CT compositional grammar expressions see Compositional Grammar - Specification and Guide.

5

In the Snowstorm service requests [snowstorm] should be replaced by the URL to the Snowstorm server endpoint.

6

In the FHIR service requests [fhir] should be replaced by the URL to the FHIR terminology server endpoint. FHIR^® is a registered trademarks of HL7 (www.hl7.org).

7

The SNOMED CT MySQL example database is not designed as a terminology server and is not intended for use in a live system . It is referenced in this guide as an illustration that some readers may find helpful. For more information about the SNOMED CT example database see the SNOMED CT - SQL Practical Guide. For instructions on how to build the example database refer to Appendix A: Building the SNOMED CT Example Database.

8

For more information about the differences between SubClass axioms and GCI axioms see General Concept Inclusions - GCIs in the Editorial Guide.

Search

4.4 Get Definition of a Concept

Overview

Notes

Requirements and Options

Notes

Interdependencies

Required By

Depends On

Service Examples

Footnotes